Question

Question 5 (1 point) Efficiency experts study the processes used to manufacture items in order to make them as efficient as possible. One of the steps used to manufacture a metal clamp involves the drilling of three holes. In a sample of 83 clamps, the mean time to complete this step was 56.6 seconds. Assume that the population standard deviation is 9 seconds. What is the lower bound of the 98% confidence interval? Round your answer to one decimal place (for example: 41.9). Write only a number as your answer.

Answer 1

Solution :

Given that,

Sample size = n = 83

Z$\alpha$ = 2.054

Margin of error = E = Z$\alpha$* ($\sigma$ /$\sqrt$n)

= 2.054 * (9 / $\sqrt$ 83)

Margin of error = E = 2.0

At 98% lower confidence level $\mu$ is

$\bar x$ - E

56.6 - 2.0

54.6

lower bound: 54.6