The true sample mean and sample standard deviation of the data are 67.8 and 18.8, respectively, rounded to one decimal place. Explain why the grouped-data formulas generally yield only approximations to the sample mean and sample standard deviation for non-single-value grouping.
Choose the correct answer below:
A. It is the result of counting data values more than once for grouped data and only once for non-grouped data.
B. It is the result of intermediate round off error in the calculations for grouped data.
C. It is the result of counting data values only once for grouped data and more than once for non-grouped data.
D. It is the result of using a class mark or midpoint to approximate data values rather than using the raw data.