The standard deviation of a normally distributed population is equal to 10. A sample size of 25 is selected, and its mean is found to be 95.
a. Find an 80% confidence interval for m.
b. What would the 80% confidence interval be for a sample of size 100?
c. What would be the 80% confidence interval for a sample of size 25 with a standard deviation of 5 (instead of 10)?