Independent variables, dependent variables, and extraneous variables

Sample Solution

Independent Variables

An independent variable is the variable that is manipulated by the researcher. It is the variable that the researcher believes will have an effect on the dependent variable. In an experiment, the independent variable is the variable that is changed by the researcher. For example, in an experiment on the effect of fertilizer on plant growth, the independent variable would be the amount of fertilizer applied to the plants.

Full Answer Section

Dependent Variables

A dependent variable is the variable that is measured by the researcher. It is the variable that the researcher believes will be affected by the independent variable. In an experiment, the dependent variable is the variable that is measured after the independent variable has been manipulated. For example, in an experiment on the effect of fertilizer on plant growth, the dependent variable would be the height of the plants.

Extraneous Variables

Extraneous variables are variables that are not controlled by the researcher and that could affect the dependent variable. They can confound the results of an experiment, making it difficult to determine the true effect of the independent variable. For example, in an experiment on the effect of fertilizer on plant growth, an extraneous variable could be the amount of sunlight the plants receive.

Controlling Extraneous Variables

There are two main ways that researchers attempt to control extraneous variables:

1. Randomization: Randomization is a statistical technique that is used to assign participants to different groups in a study. By randomly assigning participants to groups, the researcher can ensure that the groups are similar in all respects except for the independent variable. This helps to control for extraneous variables, as it ensures that any differences between the groups are likely due to the independent variable and not to other factors.

2. Matching: Matching is a research technique that is used to create groups of participants that are similar in all respects except for the independent variable. This is done by matching participants on one or more extraneous variables. For example, in an experiment on the effect of fertilizer on plant growth, the researcher could match the plants on their height