A savings and loan association needs information concerning

A savings and loan association needs information concerning the checking account balances of its local customers. A random sample of 14 accounts was checked and yielded a mean balance of $664.14 and a standard deviation of $297.29. Find a 98% confidence interval for the true mean checking account balance for local customers.

Solution

alpha = 1 - 0.98 = 0.02

alpha/2 = 0.01

df = 13

t = 2.650

I: 664.14 +/- 2.650 * 297.29 / srqt(14)

I: 664.14 +/- 210.55

453.59 < miu < 874.69