Part-time jobs, part 2.

Suppose the Dutch business school in Exercise 33 sampled 20 students having part-time jobs instead of 55, and for the sample of 20, the sample mean salary remained €1,200 with a sample standard deviation of €200.

a) What is the standard error of the mean salary?

b) What happens to the accuracy of the estimate when the interval is constructed using the smaller sample size?

c) Find and interpret a 95% confidence interval.

d) How does the margin of error for the interval constructed in Exercise 33 compare with the margin of error constructed in this exercise? Explain statistically how sample size changes the accuracy of the constructed interval.

Which sample would you prefer if you were the investigator?

Why?