Question

A random sample of 45 is taken from membership directory of a local church. The average amount given to the church by these individuals is 350 dollars every month with a sample standard deviation of 50 bucks. Construct a 90% confidence interval for the average amount given by all church members.

Answer 1

Solution :

t _/2,df = 1.680

Margin of error = E = t_/2,df * (s /n)

= 1.680 * (50 / 45)

Margin of error = E = 12.5

The 90% confidence interval estimate of the population mean is,

- E < < + E

350 - 12.5 < < 350 + 12.5

337.5 < < 362.5

(337.5 ,362.5)