#### Answer

I am 95% confident that the population average cost of doctor’s visits is between 43.15 and 46.45

#### Work Step by Step

You do not know population standard deviation, so you must use the t interval function on your calculator.
X bar : 44.80
Sx: 3.53
n:20
C-Level: .95
43.15 < $\mu$ < 46.45