Your friend, Jason, took the Graduate Record Exam in September and scored in the 98th percentile. In April, Jason took the same exam again. This time your friend scored in the 87th percentile. As a research methods student, you told your friend that his lowered score was most likely due to:

Statistical regression.

Explanation:

Statistical Regression can be defined as a technique that is used to examine that how an independent variable affects a dependent variable. In simple terms, this method helps to determine how an independent variable will bring changes in a dependent variable.

In the given case, the dependent variable is the percentage scored by Jason, whereas an independent variable will be change in period. The first time Jason took the test was in the month of September and the second exam was given in April. Because of the time gap between the two exams, there's a tendency to forget many of the things which may lower the score, from the first one.

So, the correct answer is statistical regression.

that's a true information