We could take two groups of high school students and give each one of them the same test. After randomly assigning them, one of the groups will have classical music playing during the test while the other will not. After the tests are complete, we can see which group did better (maybe some kids just cannot concentrate with noise).
Hypothesis: If high school students listen to classical music while taking a standardized test, then they will achieve better scores on that test.
The independent variable is the classical music or not.
The dependent variable is the test scores.
The subjects will be high school sophomores. There will be an equal amount of boys and girls who will then be placed in two groups through random assignment.
The experimental group will have the classical music playing while testing and the control group will not.
Some confounding variables include volume of music, length of test, and overall difficulty of test.
The two ways to control bias would be through random assignment and variation of music pieces (so one piece does not get too repetitive for any one person).