independent variable in magnet experiment

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• Independent/Dependent Variables

Definitions of Control, Constant, Independent and Dependent Variables in a Science Experiment

Why Should You Only Test for One Variable at a Time in an Experiment?

The point of an experiment is to help define the cause and effect relationships between components of a natural process or reaction. The factors that can change value during an experiment or between experiments, such as water temperature, are called scientific variables, while those that stay the same, such as acceleration due to gravity at a certain location, are called constants.

The scientific method includes three main types of variables: constants, independent, and dependent variables. In a science experiment, each of these variables define a different measured or constrained aspect of the system.

Constant Variables

Experimental constants are values that should not change either during or between experiments. Many natural forces and properties, such as the speed of light and the atomic weight of gold, are experimental constants. In some cases, a property can be considered constant for the purposes of an experiment even though it technically could change under certain circumstances. The boiling point of water changes with altitude and acceleration due to gravity decreases with distance from the earth, but for experiments in one location these can also be considered constants.

Sometimes also called a controlled variable. A constant is a variable that could change, but that the experimenter intentionally keeps constant in order to more clearly isolate the relationship between the independent variable and the dependent variable.

If extraneous variables are not properly constrained, they are referred to as confounding variables, as they interfere with the interpretation of the results of the experiment.

Some examples of control variables might be found with an experiment examining the relationship between the amount of sunlight plants receive (independent variable) and subsequent plant growth (dependent variable). The experiment should control the amount of water the plants receive and when, what type of soil they are planted in, the type of plant, and as many other different variables as possible. This way, only the amount of light is being changed between trials, and the outcome of the experiment can be directly applied to understanding only this relationship.

Independent Variable

The independent variable in an experiment is the variable whose value the scientist systematically changes in order to see what effect the changes have. A well-designed experiment has only one independent variable in order to maintain a fair test. If the experimenter were to change two or more variables, it would be harder to explain what caused the changes in the experimental results. For example, someone trying to find how quickly water boils could alter the volume of water or the heating temperature, but not both.

Dependent Variable

A dependent variable – sometimes called a responding variable – is what the experimenter observes to find the effect of systematically varying the independent variable. While an experiment may have multiple dependent variables, it is often wisest to focus the experiment on one dependent variable so that the relationship between it and the independent variable can be clearly isolated. For example, an experiment could examine how much sugar can dissolve in a set volume of water at various temperatures. The experimenter systematically alters temperature (independent variable) to see its effect on the quantity of dissolved sugar (dependent variable).

Control Groups

In some experiment designs, there might be one effect or manipulated variable that is being measured. Sometimes there might be one collection of measurements or subjects completely separated from this variable called the control group. These control groups are held as a standard to measure the results of a scientific experiment.

An example of such a situation might be a study regarding the effectiveness of a certain medication. There might be multiple experimental groups that receive the medication in varying doses and applications, and there would likely be a control group that does not receive the medication at all.

Representing Results

Identifying which variables are independent, dependent, and controlled helps to collect data, perform useful experiments, and accurately communicate results. When graphing or displaying data, it is crucial to represent data accurately and understandably. Typically, the independent variable goes on the x-axis, and the dependent variable goes on the y-axis.

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What is the independent variable in electromagnetism?

As we know, In a circuit, simple or complex, electric fields created by surface charges move electrons which creates current which creates magnetic field which can be coupled to other lines and induce voltage if it is changing by time, which also creates current and this current also creates magnetic field and voltage drop along where it is coupled so on and so forth. Voltage and electric field are related just like currents and magnetic fields are. Changing electric fields create magnetic fields and the opposite is also true. I mean what is the independent variable here? Everything is like being affected by one another continuously. Is it power or energy or fields? What variable or thing I must I hang on to or take as starting point for better analysis of circuits?

• electromagnetism
• degrees-of-freedom

• 2 $\begingroup$ You are correct. It's not "one or the other". The electromagnetic field is a single entity. If you want to understand how it behaves, then you have to look at all the field components at once. The main problem that the student discovers while learning electromagnetism is that we are trying a "gentle" introduction to it by explaining the static electric field and the static magnetic field first. This, however, is a mirage that does you disservice in the long run because your mind gets used to thinking about components of what is one single phenomenon as two different phenomena. $\endgroup$ –  FlatterMann Commented Jun 6, 2023 at 21:16
• 1 $\begingroup$ In a circuit, the "independent" variable, as you call it, can be either a voltage source or a current source. These have the same, certainly similar, role as in heat conduction the prescribed temperatures at the end of a rod. These are prescribed time varying "boundary conditions" that prescribe the current in any branch that contains no inductor, or prescribe a voltage drop between any two points not connected by a capacitor. $\endgroup$ –  hyportnex Commented Jun 6, 2023 at 21:16
• $\begingroup$ For Maxwell's equations, you can have an independently prescribed current density $\mathbf J_s$ as a volume source in $curl \mathbf H = \mathbf J + \mathbf J_s +\partial \mathbf D/\partial t$ and prescribed surface sources or, equivalently, prescribed surface values of $E$ or $H$, as is frequently done in diffraction problems. $\endgroup$ –  hyportnex Commented Jun 6, 2023 at 21:20
• $\begingroup$ Possible duplicates: Do Maxwell's Equations overdetermine the electric and magnetic fields? and links therein. $\endgroup$ –  Qmechanic ♦ Commented Jun 6, 2023 at 23:33

2 Answers 2

To frame this a slightly different way, imagine a roller coaster moving along a track. It moves in all three spatial dimensions in general. As it moves along $x$ , for example, it must also move along $y$ and $z$ in a very specific way because of the constraint of the track. So does $x$ motion cause $y$ and $z$ motion, or does $y$ motion cause $x$ and $z$ motion? Or perhaps $z$ motion causes $x$ and $y$ motion?

The answer is, of course, that viewing any one as being the primitive cause of the others is arbitrary and not particularly meaningful. They are separate degrees of freedom whose rates of change are related to one another by way of a constraint being applied.

In the rollercoaster example, it is possible to reframe the problem to eliminate the constraint. If we consider not $x,y,$ and $z$ separately but rather the distance $s$ along the track, then the constrained problem with three variables reduces to an unconstrained problem with one variable. This is one of the great advantages of the Lagrangian approach which one learns in an intermediate mechanics course.

One could ask whether it is possible to do the same with electromagnetism, and the answer is ... sort of. By reframing Maxwell's equations by introducing the scalar and vector potentials $\phi$ and $\vec A$ , the constraints relating the electric and magnetic fields are incorporated automatically, and we've dropped from six fields $(E_x,E_y,E_z,B_x,B_y,B_z)$ down to four $(\phi,A_x,A_y,A_z)$ .

However, in doing this we find a new problem - we have eliminated the constraint, but we have introduced a redundancy. If $(\phi,\vec A)$ is a solution of Maxwell's equations for a given scenario, then $(\phi',\vec A')$ is also a solution for precisely the same scenario if $$\matrix{\phi' = \phi + \frac{\partial \chi}{\partial t} \\ \vec A' = \vec A - c\nabla \chi}$$ for any scalar function $\chi$ . The solutions $(\phi',A')$ and $(\phi,A)$ are physically identical. In order to obtain a unique solution, we need to write down some criterion for choosing the one we want; this is called a choice of gauge .

So the punchline is that in electromagnetism, you may either work with the (constrained) fields or the (gauge-redundant) potentials. Unlike the mechanical case, there is no middle ground between the two.

You noticed a problem with conventional wisdom: the statement that a changing E (B) field creates a B (E) field. This is a fine way to think when designing motors and inductors, or preparing for an EMP attack, it’s not strictly true (it’s not even causal).

The independent variables are charges, currents, and their time derivatives, on the past light cone. They create electric and magnetic fields in such a way that the time derivative of one is proportional to the curl of the other. See: Jefimenko’s equation.

Whether you consider the fields fundamental or the potentials, is a whole nother debate

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Difference Between Independent and Dependent Variables

The independent and dependent variables are the two main types of variables in a science experiment. A variable is anything you can observe, measure, and record. This includes measurements, colors, sounds, presence or absence of an event, etc.

The independent variable is the one factor you change to test its effects on the dependent variable . In other words, the dependent variable “depends” on the independent variable. The independent variable is sometimes called the controlled variable, while the dependent variable may be called the experimental or responding variable.

• The independent variable is the one you control or manipulate. The dependent variable is the one that responds and that you measure.
• The independent variable is the cause, while the dependent variable is the effect.
• Graph the independent variable on the x-axis. Graph the dependent variable on the y-axis.

How to Tell the Independent and Dependent Variable Apart

Both the independent and dependent variables may change during an experiment, but the independent variable is the one you control, while the dependent variable is one you measure in response to this change. The easiest way to tell the two variables apart is to phrase the experiment in terms of an “if-then” or “cause and effect” statement. If you change the independent variable, then you measure its effect on the dependent variable. The cause is the independent variable, while the effect is the dependent variable. If you state “time spent studying affect grades” (independent variables determines dependent variable), the statement makes sense. If your cause and effect statement is in the wrong order (grades determine time spent studying), it doesn’t make sense.

Sometimes the independent variable is easy to identify. Time and age are almost always the independent variable in an experiment. You can measure them, but you can’t control any factor to change them.

Ask yourself these questions to help tell the two variables apart:

Independent Variable

• Can you control or manipulate this variable?
• Does this variable come first in time?
• Are you trying to tell whether this variable affects an outcome or answers a question?

Dependent Variable

• Does this variable depend on another variable in the experiment?
• Do you measure this variable after controlling another factor?

Examples of Independent and Dependent Variables

For example, if you want to see whether changing dog food affects your pet’s weight, you can phrase the experiment as, “If I change dog food, then my dog’s weight may change.” The independent variable is the type of dog food, while the dog’s weight is the dependent variable.

In an experiment to test whether a drug is an effective pain reliever, the presence, absence, or dose of the drug is the variable you control (the independent variable), while the pain level of the patient is the dependent variable.

In an experiment to determine whether ice cube shapes determine how quickly ice cubes melt, the independent variable is the shape of the ice cube, while the time it takes to melt is the dependent variable.

If you want to see if the temperature of a classroom affects test score, the temperature is the independent variable. Test scores are the dependent variable.

Graphing Independent and Dependent Variables With DRYMIX

By convention, the independent variable is plotted on the x-axis of a graph, while the dependent variable is plotted on the y-axis. Use the DRY MIX acronym to remember the variables:

D is the dependent variable R is the variable that responds Y is the y-axis or vertical axis

M is the manipulated or controlled variable I is the independent variable X is the x-axis or horizontal axis

• Carlson, Robert (2006).  A Concrete Introduction to Real Analysis . CRC Press.
• Edwards, Joseph (1892).  An Elementary Treatise on the Differential Calculus  (2nd ed.). London: MacMillan and Co.
• Everitt, B. S. (2002).  The Cambridge Dictionary of Statistics  (2nd ed.). Cambridge UP. ISBN 0-521-81099-X.
• Hinkelmann, Klaus; Kempthorne, Oscar (2008). Design and Analysis of Experiments. Volume I: Introduction to Experimental Design (2nd ed.). Wiley. ISBN 978-0-471-72756-9.
• Quine, Willard V. (1960). “ Variables Explained Away “.  Proceedings of the American Philosophical Society . American Philosophical Society. 104 (3): 343–347. 

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Make a Magnet

Introduction: (initial observation).

The discovery of magnetism has had a very important role in human life and modern technology. Magnets are an essential part of electric motors and generators. Without magnets, electric generators could not produce electricity. Things that would disappear if we had no electricity are telephones, lights, electric heat, computers, televisions. The fact that an invisible magnetic force is able to attract or repel certain metals is enough interesting for a science project.

Magnets can be made by placing a magnetic material such as iron or steel, in a strong magnetic field. Permanent and temporary magnets can be made in this manner.

Dear This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “ How to Start ” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Information Gathering:

Find out about magnets and magnetism. Click here for some online information. Also read books, magazines or ask professionals who might know in order to learn about making magnets, uses of magnets and factors that may affect the strength of a magnet. Keep track of where you got your information from.

Following are samples of information that you may find.

As magnetic substances are able to retain magnetism for different periods of time that range from a very short period of time to a very long period of time, magnetic substances are used for making magnets. There are some magnetic substances that are good for making temporary magnets, and some for making permanent magnets. Iron and Steel are two of the magnetic substances which can be used to make magnets. Before we proceed to learn how to make magnets, let us first learn about the properties of Iron and Steel .

Properties of Iron and Steel

Magnets can be made by using several methods. The most commonly used methods are as given below:

Single Touch Method

The single touch method involves the usage of only one magnet and a steel bar. In order for the magnet to be a permanent magnet, a steel bar is used. As shown in Figure (a), bar AB represents the steel bar.

• The bar magnet (with north pole in this figure) is placed at end A if the steel bar, and moved towards end B without lifting the magnet.
• Once it reaches end B of the steel bar, the magnet is lifted and placed at end A and moved towards end B in the same direction as before.
• Steps 1 and 2 are repeated at least 30 times. This method of moving the magnet over the steel bar is referred to as rubbing the steel bar or stroking the steel bar with the magnet. The steel bar should be rubbed with the magnet in the same direction, otherwise the steel bar will not get magnetized.

Fig. (a)Single Touch Method

In this case (Fig. a) while rubbing the steel bar with the North pole from end A to end B, end A of the steel bar becomes the North pole while end B of the steel bar becomes the South pole.

Double Touch Method

Fig (b). Double Touch Method

The double touch method involves the usage of two magnets and a steel bar. In order for the magnet to be a permanent magnet, a steel bar is used. As shown in Figure (b), bar AB represents the steel bar.

• The two bar magnets with opposite poles facing each other are first placed at the center of the steel bar.

2. The bar magnets are then moved towards the ends of the steel bar without lifting the magnets. 3. Once the magnets reach the ends of the steel bar, the magnets are lifted and placed again at the center of the steel bar, and moved towards the ends in the same direction as before. 4. Steps 1 to 3 are repeated at least 30 times.

In this case (Fig. b), rubbing the steel bar using two magnets with opposite poles facing each other as shown in Fig. (b), end A of the steel bar becomes the North pole while end B of the steel bar becomes the South pole.

Note: It must be borne in mind that since steel is very hard to magnetize, it may be required to stroke the steel bar for a long period of time. Iron on the other hand is very easy to magnetize. However, iron loses its magnetism very quickly.

Electromagnet

The following equipments are required in order to make an electromagnet:

• Iron object such as iron nail or iron bar
• Insulated copper wire
• 1.5 volts or 3.0 volts battery/cell
• iron paper clips or iron filings

Fig. (c). An Electromagnet

• Take any iron object such as an iron nail.
• Wind an insulated copper wire around the iron nail about 100 times.
• Remove the insulation from about 1 cm (1/2 inch) of each end of the wire.
• Now connect one free end of the wire to the positive terminal of a battery/cell, and the other free end of the insulated wire to the negative end of the battery/cell, as shown in Fig (c).
• Try bringing some iron filings or pins at any end of the iron object that is getting magnetized. What do you think might happen?

Once the circuit is completed by connecting the free ends of the wire to the terminals of the battery/cell, electric current starts flowing through the wire from the positive terminal to the negative terminal. This generates a magnetic field around it and the iron nail gets magnetized. It starts behaving like a magnet so as long as the electric current flows through the wire. At this point of time, if any magnetic substance is brought close to the iron nail, the magnetic substance will get attracted to the iron nail and cling to it so as long as the nail remains magnetized or retains its magnetism. Once the the flow of electric current through the insulated wire is stopped, the pins or iron filings will fall off the nail provided the nail is made of iron. If the nail is made of steel then the nail will retain some magnetism and the pins will not fall off.

Note: Replacing the iron nail with a steel nail will give you a permanent magnet.

Strength of the electromagnet

The strength of an electromagnet can be increased by:

• Increasing the number of turns
• Increasing the voltage of the battery.
• Using iron instead of steel

Circuit: Route laid out with wires which connect circuit components along which the electrical current flows. Compass: An instrument that is used to find/determine the North-South directions. It is often used for navigational purposes.

Current: Flow of electrons through a wire

Displacement: Change in position in a given direction

Energy: Capacity to do work

Force: Defined as push or pull

Magnetic substances: Substances that get attracted to magnet and can be magnetized

Magnetic field: Area around a magnet.

Magnetite: A natural form of magnet

Poles: The two ends of a magnet that have maximum forces of attraction.

Solar wind: Stream of ionized gases that blows outward from the Sun with varying intensity that depends on the amount of surface activity on the Sun.

Turns: the number of times a wire is wound around an object such as a nail or bar.

Work: Product of force and displacement in the direction of the force

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to learn about magnets and how they are made. Specific question that can be studied in this project is:

• How can you make an Iron nail to become a magnet? and which method of making magnet creates a stronger magnet?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Depending on the question that you choose to study, you may define different variables or factors that are being studied.

For the main question of this project, this is how you may define variables:

• Independent variable (also known as manipulated variable) is the method of making magnet.
• Dependent variable (also known as responding variable) is the strength of magnet that can be made. The strength can be measured by the amount of iron filings of small nails that the magnet can lift.

If you are doing this as a display project, you may not be required to define variables and to perform multiple experiments.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. For example if you want to make magnet using electricity, following are some possible hypothesis.

• Making magnet using electricity produces a stronger magnet in compare with magnets that are made by rubbing against another magnet.
• While using electricity to make magnet, more electricity (stronger battery, higher Voltage and Current) can make stronger magnet.
• While using electricity to make magnet, more loops on the coil of wire can create stronger magnets.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1: Making magnets using electricity

Introduction:

In this experiment you will magnetize a few identical nails with different methods as described in the gathering information section. If you are doing a display project, that is all you need to do as your experiment; otherwise you need to compare the strength of magnets made in different methods.

Get some magnet wire (or any other single strand insulated wire) and wrap it around a nail. Connect the two ends of the wire to the battery set. Use some paper clips to see if your nail is magnetized. What you have made is an electromagnet.

Magnet wire is a regular copper wire with a thin coating of an insulating material. You need to remove the coating from both ends of your wire in order to create a good contact with your battery poles (Or battery holder wires). The coating of magnetic wire is a special type of resin that can be removed by scratching with a sharp object or sand paper. You should get a good result if you have wrapped your magnet wire at least 20 times or more around the nail.

Now use a compass or another magnet with marked poles. Test to see which side of the nail is the North Pole and which side is the South Pole of your magnet. Switch the battery poles and see if it affects the North/South Poles of your magnet. You can also change the direction of the wrapping of the wire to see the effect of that on North and South Poles of your electromagnet.

Most nails will become a permanent magnet after such experiment. In other words a strong magnetic field created by the coil and the battery can change a regular steel nail to a permanent magnet .

So remove the coil of wire from around the nail and see if the nail has enough magnetic force to lift a small paper clip or a small needle.

You can try different types of nail and compare the results.

Experiment 2: Make magnet using touching or rubbing method

One of the methods to make a magnet is the touch method or rubbing method. This method is described in the gathering information section (above) in detail. For example you can magnetize a nail or needle by rubbing it with a strong magnet. As a mater of fact, even placing a strong magnet close to a nail for a few seconds can induce some magnetic properties on the nail. For this reason, many nails and other steel objects around you may already have some magnetic properties.

Mark one end of the needle with a marker (optional). Magnetize the needle by rubbing it with a strong magnet (single touch method) for 1 minute.

To see if your needle is really magnetized, use it to make a compass as described below:

Make a Compass

Insert the needle in a small cork or small piece of Styrofoam.

Fill up a cup with water. It helps if you overfill the water so the water level will be above the edges of the cup.

Float the needle carefully in the center of the water.

Does the needle move and then stay in a specific north/south direction?

Overfilling the cup with water makes the needle stay in the center, otherwise it will move to the side.

Change the direction of needle and then release it again. Does it move back to the north/south direction?

Experiment 3: Comparing methods of making magnet

• Get 5 identical large nails and number them from 1 to 5.
• Use touch method to magnetize the nail number 1 for 1 minute.
• Use a coil of 50 turns wire and a 1.5 volt battery to magnetize the nail number 2 for 1 minute.
• Use a coil of 100 turns wire and a 1.5 volt battery to magnetize the nail number 3 for 1 minute.
• Use a coil of 50 turns wire and a 3 volt battery to magnetize the nail number 4 for 1 minute.
• Do not do anything with the nail number 5 and keep it as control.
• Test all the nails to find out the maximum iron filing that they can lift.Record your results in a table like this:

As a 3 volt battery, you may connect two 1.5 volt batteries in series (One behind the other).

4″ common nails or larger may be used for this experiment.

Materials and Equipment:

To make electromagnet you need a 6 volts battery. Hardware stores sell special 6 volts batteries known as lantern battery. You can also connect 4 flashlight batteries using a battery holder to get 6 volts. List of material including optional items is here:

• Battery Holder (for 2 or 4 flashlight batteries of any size)
• Insulated wire (Gage 24, also known as thermostat wire)
• One Iron nail (2″ or 3″) or similar metal rod.
• A strong magnet.
• Some Iron filings, pins or paper clips to test the magnet.
• A small compass to test the magnet poles.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

No calculation is required.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List of References

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Methodology

• Independent vs. Dependent Variables | Definition & Examples

Independent vs. Dependent Variables | Definition & Examples

Published on February 3, 2022 by Pritha Bhandari . Revised on June 22, 2023.

In research, variables are any characteristics that can take on different values, such as height, age, temperature, or test scores.

Researchers often manipulate or measure independent and dependent variables in studies to test cause-and-effect relationships.

• The independent variable is the cause. Its value is independent of other variables in your study.
• The dependent variable is the effect. Its value depends on changes in the independent variable.

Your independent variable is the temperature of the room. You vary the room temperature by making it cooler for half the participants, and warmer for the other half.

Table of contents

What is an independent variable, types of independent variables, what is a dependent variable, identifying independent vs. dependent variables, independent and dependent variables in research, visualizing independent and dependent variables, other interesting articles, frequently asked questions about independent and dependent variables.

An independent variable is the variable you manipulate or vary in an experimental study to explore its effects. It’s called “independent” because it’s not influenced by any other variables in the study.

Independent variables are also called:

• Explanatory variables (they explain an event or outcome)
• Predictor variables (they can be used to predict the value of a dependent variable)
• Right-hand-side variables (they appear on the right-hand side of a regression equation).

These terms are especially used in statistics , where you estimate the extent to which an independent variable change can explain or predict changes in the dependent variable.

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There are two main types of independent variables.

• Experimental independent variables can be directly manipulated by researchers.
• Subject variables cannot be manipulated by researchers, but they can be used to group research subjects categorically.

Experimental variables

In experiments, you manipulate independent variables directly to see how they affect your dependent variable. The independent variable is usually applied at different levels to see how the outcomes differ.

You can apply just two levels in order to find out if an independent variable has an effect at all.

You can also apply multiple levels to find out how the independent variable affects the dependent variable.

You have three independent variable levels, and each group gets a different level of treatment.

You randomly assign your patients to one of the three groups:

• A low-dose experimental group
• A high-dose experimental group
• A placebo group (to research a possible placebo effect )

A true experiment requires you to randomly assign different levels of an independent variable to your participants.

Random assignment helps you control participant characteristics, so that they don’t affect your experimental results. This helps you to have confidence that your dependent variable results come solely from the independent variable manipulation.

Subject variables

Subject variables are characteristics that vary across participants, and they can’t be manipulated by researchers. For example, gender identity, ethnicity, race, income, and education are all important subject variables that social researchers treat as independent variables.

It’s not possible to randomly assign these to participants, since these are characteristics of already existing groups. Instead, you can create a research design where you compare the outcomes of groups of participants with characteristics. This is a quasi-experimental design because there’s no random assignment. Note that any research methods that use non-random assignment are at risk for research biases like selection bias and sampling bias .

Your independent variable is a subject variable, namely the gender identity of the participants. You have three groups: men, women and other.

Your dependent variable is the brain activity response to hearing infant cries. You record brain activity with fMRI scans when participants hear infant cries without their awareness.

A dependent variable is the variable that changes as a result of the independent variable manipulation. It’s the outcome you’re interested in measuring, and it “depends” on your independent variable.

In statistics , dependent variables are also called:

• Response variables (they respond to a change in another variable)
• Outcome variables (they represent the outcome you want to measure)
• Left-hand-side variables (they appear on the left-hand side of a regression equation)

The dependent variable is what you record after you’ve manipulated the independent variable. You use this measurement data to check whether and to what extent your independent variable influences the dependent variable by conducting statistical analyses.

Based on your findings, you can estimate the degree to which your independent variable variation drives changes in your dependent variable. You can also predict how much your dependent variable will change as a result of variation in the independent variable.

Distinguishing between independent and dependent variables can be tricky when designing a complex study or reading an academic research paper .

A dependent variable from one study can be the independent variable in another study, so it’s important to pay attention to research design .

Here are some tips for identifying each variable type.

Recognizing independent variables

Use this list of questions to check whether you’re dealing with an independent variable:

• Is the variable manipulated, controlled, or used as a subject grouping method by the researcher?
• Does this variable come before the other variable in time?
• Is the researcher trying to understand whether or how this variable affects another variable?

Recognizing dependent variables

Check whether you’re dealing with a dependent variable:

• Is this variable measured as an outcome of the study?
• Is this variable dependent on another variable in the study?
• Does this variable get measured only after other variables are altered?

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Independent and dependent variables are generally used in experimental and quasi-experimental research.

Here are some examples of research questions and corresponding independent and dependent variables.

For experimental data, you analyze your results by generating descriptive statistics and visualizing your findings. Then, you select an appropriate statistical test to test your hypothesis .

The type of test is determined by:

• your variable types
• level of measurement
• number of independent variable levels.

You’ll often use t tests or ANOVAs to analyze your data and answer your research questions.

In quantitative research , it’s good practice to use charts or graphs to visualize the results of studies. Generally, the independent variable goes on the x -axis (horizontal) and the dependent variable on the y -axis (vertical).

The type of visualization you use depends on the variable types in your research questions:

• A bar chart is ideal when you have a categorical independent variable.
• A scatter plot or line graph is best when your independent and dependent variables are both quantitative.

To inspect your data, you place your independent variable of treatment level on the x -axis and the dependent variable of blood pressure on the y -axis.

You plot bars for each treatment group before and after the treatment to show the difference in blood pressure.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

• Normal distribution
• Degrees of freedom
• Null hypothesis
• Discourse analysis
• Control groups
• Mixed methods research
• Non-probability sampling
• Quantitative research
• Ecological validity

Research bias

• Rosenthal effect
• Implicit bias
• Cognitive bias
• Selection bias
• Negativity bias
• Status quo bias

An independent variable is the variable you manipulate, control, or vary in an experimental study to explore its effects. It’s called “independent” because it’s not influenced by any other variables in the study.

A dependent variable is what changes as a result of the independent variable manipulation in experiments . It’s what you’re interested in measuring, and it “depends” on your independent variable.

In statistics, dependent variables are also called:

Determining cause and effect is one of the most important parts of scientific research. It’s essential to know which is the cause – the independent variable – and which is the effect – the dependent variable.

You want to find out how blood sugar levels are affected by drinking diet soda and regular soda, so you conduct an experiment .

• The type of soda – diet or regular – is the independent variable .
• The level of blood sugar that you measure is the dependent variable – it changes depending on the type of soda.

No. The value of a dependent variable depends on an independent variable, so a variable cannot be both independent and dependent at the same time. It must be either the cause or the effect, not both!

Yes, but including more than one of either type requires multiple research questions .

For example, if you are interested in the effect of a diet on health, you can use multiple measures of health: blood sugar, blood pressure, weight, pulse, and many more. Each of these is its own dependent variable with its own research question.

You could also choose to look at the effect of exercise levels as well as diet, or even the additional effect of the two combined. Each of these is a separate independent variable .

To ensure the internal validity of an experiment , you should only change one independent variable at a time.

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What are the Independent/Dependent/Controlled Variables

Moderators: kgudger , Moderators

Post by Panina » Tue Dec 30, 2014 12:46 pm

Re: What are the Independent/Dependent/Controlled Variables

Post by tdaly » Fri Jan 02, 2015 10:32 am

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