Suppose a 99% Confidence Interval for ? Turns Out to Be

Multiple Choice

Suppose a 99% confidence interval for ? turns out to be (1000,2100) .If this interval was based on a sample of size n=23,explain what assumptions are necessary for this interval to be valid.

A) The sampling distribution of the sample mean must have a normal distribution.
B) The sampling distribution must be biased with 22 degrees of freedom.
C) The population of salaries must have an approximate t distribution.
D) The population must have an approximately normal distribution.