Suppose a 98% confidence interval for μ turns out to be

If this interval was based on a sample of size

explain what assumptions are necessary for this interval to be valid.
◦ The sampling distribution of the sample mean must have a normal distribution.
◦ The population must have an approximately normal distribution.
◦ The sampling distribution must be biased with 21 degrees of freedom.
◦ The population of salaries must have an approximate t distribution.