You are told that a random sample of 150 people from Manchester New Hampshire have been given cholesterol tests, and 60 of these people had levels over the safe count of 200.

Using Excel, construct a 95% confidence interval for the population proportion of people in New Hampshire with cholesterol levels over 200.

Note: Note that this question requires confidence interval for a proportion, the interval that is likely to capture the proportion of all population members that satisfy a specified property. Do you remember the formula? If not, here it is:

p estimate + – z-critical value X sqrt (p estimate (1-p estimate)/n)

Also note that, for population proportion, we use z-multiple not the t-multiple. So you can ask, where is the population standard deviation? You don’t need it. Look at the formula.