The lifetime (in hours) of a 60-watt light bulb is a random variable that has a normal distribution with σ = 30 hours. a random sample of 25 bulbs put on test produced a sample mean lifetime of = 1038. construct a 92% confidence interval estimate for the mean lifetime μ. if it were desired to cut the confidence interval to half its length while keeping the same 92% level, what size sample would be required to achieve this?

a) 92% Confidence interval: (1027.5,1048.5)

b) Sample size = 100

Step-by-step explanation:

We are given the following in the question:

Sample mean, = 1038

Sample size, n = 25

Alpha, α = 0.08

Population standard deviation, σ = 30

a) 92% Confidence interval:

Putting the values, we get,

b) In order to reduce the confidence interval by half, we have to quadruple the sample size.

Thus,

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step-by-step explanation:

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step-by-step explanation:

2 tens + 6 ones

1 ten + 16 ones

0 tens + 26 ones