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# Confidence interval and t test for mean life time

Always get overwhelmed by the amount of material when covered at a comprehensive level. Attached is the study material of what to be prepared to cover at the conclusion of this course. I have worked through them but get stumped at several points. Can you provide a systematic approach to these problems and provide a reference to refer to make sure my solutions are accurate. It would helpful if you can explain why you did what you did, as this is just a helpful of study and questions may appear differently at the actual conclusion of the course.

GE fluorescent bulbs have a useful lifetime which is normally distributed. We wish to estimate mean lifetime. A random sample of 20 bulbs yields the following results: sample mean= 2,360 hours and a sample standard deviation of 365 hours.
Refer to Table 8B on the Handout for MegaStat output.

Part A
Analyze the output above to determine the 95% confidence interval for the mean lifetime of GE fluorescent bulbs. Interpret this confidence interval.

Part B
Suppose a GE executive says. "Our florescent bulbs have an average expected lifetime of 2500 hours." Could the executive be correct? Explain.

#### Solution Summary

Step by step method for testing the hypothesis and construction confidence interval for mean are discussed here. Excel template for each problem is also included. This template can be used to obtain the answers of similar problems.

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