We take a random sample of 7 tablet computers, and measure the time until their

Question

We take a random sample of 7 tablet computers, and measure the time until their screens become scratched or cracked (in months). The following are our observations 9.3, 9.2, 9.9, 10.1, 9.1, 9.5, 9.4 Assume that the times until being scratched or cracked are approximately normally distributed. Let ? be the true mean time (in months) until tablet screens become cracked or scratched. If we test the research hypothesis that the true mean is greater than 9, what would be the probability distribution we would use to calculate our p-value? Select one: a.ts ? c, none of the above e.t7

Explanation / Answer

Correct Choice : d. Z

Explanation:

If the population is normally distributed with mean ? and standard deviation ?, then the sampling distribution of the sample mean is also normally distributed no matter what the sample size is.

In our case, the random variable of interest is "Time until screen is scratched" , say X. It is given that X is approximately normal. So Sampling distribution of sample mean X_bar will be Normal. And also, in calculation for p-value, we need the Sampling distribution of Sample mean X_bar. Therefore, correct choice is d. Z

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