The time to failure of a light bulb, in weeks, has standard deviation 10. A rand

Question

The time to failure of a light bulb, in weeks, has standard deviation 10. A random sample of 36 light bulbs was examined until each light bulb stopped working. The sample mean time to failure is 40. Now assume the standard deviation is not known. Instead, you are given the sample variance is 121. Recalculate parts (a), (b), and (d) given this new information. Below is a correct and an incorrect interpretation of the part (a) confidence interval, where "(lower, upper)" is used in place of the answer. Identify which is correct, and briefly state why the other is incorrect. There is a 90% probability that a light bulb's mean time to failure is between (lower, upper). (lower, upper) is an interval such that 90% of similar intervals will include a light bulb's mean time to failure.

Explanation / Answer

e. a,b and d are not given

f. confidence interval is range of values so defined that there is a specified probability that the value of a parameter lies within it.

So ii is correct answer.

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