Time spent using e-mail per session is normally distributed, with mu equals =13 minutes and sigma equals

Time spent using e-mail per session is normally distributed, with mu equals μ=13 minutes and sigma equals σ=2 minutes. 

Complete parts (a) through (d). 

a. If you select a random sample of 50sessions, what is the probability that the sample mean is between 12.8 and 13.2 minutes? 

b. If you select a random sample of 50sessions, what is the probability that the sample mean is between 12.5 and 13 minutes? 

c. If you select a random sample of 100sessions, what is the probability that the sample mean is between 12.8 and 13.2 minutes? 

d. Explain the difference in the results of (a) and (c). 

Choose the correct answer below. The sample size in (c) is greater than the sample size in (a), so the standard error of the mean (or the standard deviation of the samplingdistribution) in (c) is ▼ less greater than in (a). As the standard deviation ▼ increases decreases , values become ▼ less more concentrated around the mean. Therefore, the probability of a region that includes the mean will always ▼ decrease increase when the sample size increases.

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