Independent variables are variables that are manipulated or are changed by researchers and whose effects are measured and compared. The independent variables are called as such because independent variables predict or forecast the values of the dependent variable in the model.

The variables in a study of a cause-and-effect relationship are called the independent and dependent variables. The independent variable is the cause. The dependent variable is the effect. Its value depends on changes in the independent variable.

An easy way to think of independent and dependent variables is, when you’re conducting an experiment, the independent variable is what you change, and the dependent variable is what changes because of that. You can also think of the independent variable as the cause and the dependent variable as the effect.

Independence two jointly continuous random variables X and Y are said to be independent if fX,Y (x,y) = fX(x)fY (y) for all x,y. It is easy to show that X and Y are independent iff any event for X and any event for Y are independent, i.e. for any measurable sets A and B P( X ∈ A ∩ Y ∈ B ) = P(X ∈ A)P(Y ∈ B).

The first component is the definition: Two variables are independent when the distribution of one does not depend on the the other. If the probabilities of one variable remains fixed, regardless of whether we condition on another variable, then the two variables are independent.

If an experiment compares an experimental treatment with a control treatment, then the independent variable (type of treatment) has two levels: experimental and control. If an experiment were comparing five types of diets, then the independent variable (type of diet) would have 5 levels.

For the earlier plant experiment, “How Plants Grow In Response to Light,” the growth of the plant is the dependent variable being observed The plant growth is in response to changes in the amount of light the plant receives, is the independent variable.

The variable that affects the dependent variable is called the independent variable. In the plant experiment, the independent variable could be fertilizer—some plants will get fertilizer, others will not.

In research design, independent variables are those that a researcher can manipulate, whereas dependent variables are the responses to the effects of independent variables. By purposefully manipulating the value of an independent variable, one hopes to cause a response in the dependent variable.

Explanation: Descriptive studies only describe the current state of a variable, so there are no presumed cause or effects, therefore no independent and dependent variables.

Categorical variables

The key variables are the major terms to use when searching for research articles for the Literature Review. The key variables are the terms to be operationally defined if an Operational Definition of Terms section is necessary. The key variables provide focus to the Methods section.