Final answer:
The sample mean is more efficient than the sample median since the mean of a sampling distribution of the means is approximately the mean of the data distribution, especially when the sample size is large.
Step-by-step explanation:
The correct answer is a. The sample mean is relatively more efficient than the sample median. This is true because the mean of a sampling distribution of the means is approximately the mean of the data distribution. When the sample size is large, the mean is more efficient due to the properties of the Central Limit Theorem, which states that the larger the sample, the closer the sampling distribution of the means becomes to a normal distribution. As for the other options, c is somewhat misleading, as it compares measures of dispersion, which are different concepts: sample variance is a squared quantity of variation among data points, while standard deviation is the square root of the variance, addressed directly in comparison to variance.