1. A sample of size n = 22 is taken from a population of scores. The sample mean

is 60. Show the difference between the 99% confidence interval constructed in

each of these cases:

(a) you know the standard deviation of the population is 10,

(b) you do not know the population standard deviation, but you know s =10.

2. You have ten observations on the variable "number of hours studied the night

before first midterm exam": 2, 1.5, 3, 2, 3.5, 1, 0.5, 3, 2, 4

(a) Construct the 95% confidence interval for the population mean.

(b) Construct the 90% confidence interval for the population mean.

3. How does sample size affect the width of a confidence interval (all else being

equal) when the population standard deviation is not known? (Hint: Look at the CI

formula in detail!)