In an experimental study looking at classical music exposure and reading ability in children, the researcher divided the children into two groups (Groups A and B). In Group A, the children listened to Mozart for one hour every day for one month. In Group B, parents were instructed to refrain from playing classical music around the child for one month. At the end of the month, all children were given a reading comprehension test. Those who listened to Mozart daily (Group A) scored significantly higher on the reading test. In this research study, is the Independent Variable.

In this research study children being exposed to Mozart's music is the Independent Variable.

Explanation:

First of all, a variable is an attribute, feature or element that is likely to "vary" or change. When doing an experiment or research, the two main variables are the independent and dependent variables. The independent variable is the one being manipulated by the researcher, that means the one that is changed and/or controlled during the experiment.; and the dependent variable or outcome variable, as it´s name suggests, is the outcome that is measured in the experiment. So in the example shown in this question, the children being exposed to Mozart's music is the Independent variable (the one being manipulated), because it's something that the tester can manipulate or change. And the result of the reading comprehension test is the dependable variable, which is the variable that changes due to the independent variable.