Question

A random sample of 45 cars in the drive thru of a popular fast food restaurant revealed an average bill of $19.47 per car. The population standard deviation is $6.15. Estimate the mean bill for all cars from the drive thru with 94% confidence. Round intermediate and final answers to two decimal places.

Answer 1

Answer:

The confidence interval is (17.73, 21.29)

Step-by-step explanation:

Sample size = 45

Sample mean = $19.47

Standard deviation = $6.15

Confidence Interval level = 94%, so 1 - 0.94 = 0.06

0.06/2 = 0.03 .

z(0.03) = 1.88

Margin of Error = 1.88 * 6.15/sqrt(45)

= 1.72

Confidence Interval = (19.47 - (1.88*6.15/sqrt(45)), 19.47 + (1.88*6.15/sqrt(45))

= (17.75, 21.19)