A Fourth Grade Class of 28 Students Is Given a Standardized

A fourth grade class of 28 students is given a standardized math test, both at the beginning of the semester and again at the end of the semester. The mean scores from the beginning and the end are compared. Which statistic is being studied?

A) $\overline{x}$
B) $\overline{d}$
C) $\overline{x}_{1}$ - $\overline{x}_{2}$
D) $\mu$ ₁ - $\mu$ ₂