A study is designed to test the effect of noise levels on the exam performance of students. The researcher gathers 150 male students and 150 female students from the same psychology course and randomly assigns each student to take an exam in a room with one of three noise treatments: no noise, construction noise, and human chatter (talking) noise. What is the blocking variable in this study?

The blocking variable in this study is gender of students.

Step-by-step explanation:

Remember that blocking variable is a categorical variable that is used to control the source of variation. We can control the source of variation if we categorize the subjects (in your case students) by male, by age, by race, etc.

All the demographic variables that can be created as categorical variable are blocking variables to remove the sourve of variation, these demographic variables are observed and unchanging, thats why they are very important if you want to control the variation of your study.

Remember that female and male have different behaviors, so its something that we can control if you separate female subjects from male subjects so we can see the statistical results of this study