In a simple random sample of 40 electronic components produc

In a simple random sample of 40 electronic components produced by a certain method, the mean lifetime was 1178 hours. Assume that component lifetimes are normally distributed with population standard deviation 59 hours. What is the upper bound of the 95% confidence interval for the mean lifetime of the components?

Round your answer to the nearest integer. Write only a number as your answer. The ZInterval command on the TI-84 PLUS Calculator will compute the confidnece interval for the mean when the population standard deviation is known.

Solution

Here sample mean =1178 and sigma = 59 hours

n = 40

95% confidence interval (using calculator for means)(z = 1.96, -1.96)

Lower bound =1159.72

Upper bound = 1196.28

Confidence interval =

(1159.72, 1196.28)