Answer:
Step-by-step explanation:
We want to determine a 95% confidence interval for the population mean.
Number of sample, n = 56
Mean, u = 645 hours
Standard deviation, s = 31 hours
For a confidence level of 95%, the corresponding z value is 1.96.
We will apply the formula
Confidence interval
= mean ± z ×standard deviation/√n
It becomes
645 ± 1.96 × 31/√56
= 645 ± 1.96 × 4.142
= 645 ± 8.12
The lower end of the confidence interval is 645 - 8.12 =636.88
The upper end of the confidence interval is 645 + 8.12 =653.12
Therefore, with 95% confidence interval for the population mean life of fluorescent light bulbs is between 636.88 hours and 653.12 hours
