Answer:
Step-by-step explanation:
Given are four options and we have to select the one which is suitable for mu_d.
In statistics population values are called parameters and sample values statistic.
mu represents the mean of the population and hence a parameter
mu_d is the parameter used for the difference for two populations.
Whenever two sets of data are there in population the mean of differences is called average for differences and denoted by parameter mu_d.
Hence here D. The mean of the differences from the population of matched data is right answer
