A Random Sample of 15 High School Students Is Selected $\overline{d}$

Multiple Choice

A random sample of 15 high school students is selected for a small experiment in which they will be tested in two ways: a written test and an oral exam. To avoid order effects, eight students are randomly selected to first take the written test and then the oral exam. The remaining 7 students take the tests in reverse order. Summary statistics for the two tests are provided below. What is the standard error of $\overline{d}$ ?

A) 0.145
B) 0.517
C) 0.563
D) 0.660