Science Answer: The Dependent Variable is the Variable that changes automatically during the experiment when the Independent Variable is changed by somebody.:D Read More share. A failure to isolate the controlled variables, in any experimental design, will seriously compromise the internal validity. This oversight may lead to confounding.
Dependent VariableDependent Variable:A dependent variable is what you measure in the experiment and what is affectedduring the experiment. The dependent variable responds to the independent variable.It is called dependent because it 'depends' on the independent variable.In a scientific experiment, you cannot have a dependent variable without anindependent variable.Example: You are interested in how stress affects heart rate in humans. Yourindependent variable would be the stress and the dependent variable would bethe heart rate. You can directly manipulate stress levels in your human subjectsand measure how those stress levels change heart rate.
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The Experiment VariablesOur experiment involves takingsheets of glass and coating them with sunscreen lotion of different SPFratings, then placing the coated sheets of glass under bright sunlight andtaking a UV reading behind the coated glass.In our example, you would set up severalidentical experiments (called 'controls') with only the SPF ratingchanged. The other variables for the experiment, such as the brand of thesunscreen lotion, the quantity of sunscreen lotion used for each experiment,the type of materials and the type of UV meter used for each experiment, and thetemperature, lighting conditions and humidity of the place where the experimentis conducted, must be kept the same for every experiment. You have to performthe experiment within a small window of time, under the hot sun and when thereare no clouds. You should also make sure to purchase all of the lotion from thesame pharmacy, and to purchase the lotion at the same time (just in casedifferent batches of the same brand of lotion are manufactured with differentspecifications).
The same UV meter should be used for each control experiment,as different meters (even though they are of the same brand/model) may producedifferent results due to many possible reasons (for example, the batteries mayhave run out in one UV meter, but not the other). Watch out!All scientific theory must be substantiatedby reproducible test results. These tests must be reproducible by other people.That is why it is so important for you to keep good, systematic records of yourexperiment!As you perform your experiment, you need towatch out for the following types of errors or mistakes:1. Errors in the measuring instruments that you are using.Because this type of error will always produce a measurement that is higher or lowerthan the 'true' value, it is called random error.2. Systematic errors (also known as non-random errors), which are due to factors which biasthe results of your experiment in one direction. As you design your experimentprocedure, you need to identify the independent variable, and how to measurehow the changes in the independent variable affects the dependentvariable.
Bear in mind that there canonly be one independent variable. All other variables must remain constant.This is the ensure that any changes inthe dependent variable can be properly attributed to changes in the independentvariable. In our example, we need toascertain how changes in SPF ratings affect the level of protection. If youdon't keep all other factors constant during the experiment, other than the SPFlevel (for example, if one control experiment was done under bright sunlightwhilst another is done late in the evening during sunset), you won't be in theposition to say that the results which you observed were caused by the changesin SPF levels.
Your procedure should also specify how many trials are to beperformed. At a minimum, you should repeat your experiment three times,although there's nothing to prevent you from repeating more. For experimentsthat involve surveys, there's no sense in asking the same person the samequestion more than once - however, for this type of experiment, you shouldensure that you survey a large number of participants for more reliableresults.