The Sample Mean Number of Accidents Is to Be Calculated $\overline{x}$

The sample mean number of accidents is to be calculated for a sample of husbands and wives and we wish to determine the difference in mean number of accidents for these husband-wife couples. Which statistic is being studied?

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