a. To reduce the variation in average HALT scores, an engineer advised doubling the sample size, from 20 to 40. What is the effect of doubling the sample size on the sampling distribution of the mean?...

a. To reduce the variation in average HALT scores, an engineer advised doubling the sample size, from 20 to 40. What is the effect of doubling the sample size on the sampling distribution of the mean? What properties of the sampling distribution stay the same? What changes?
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b. The amount spent by customers in the express lane of a supermarket averages
, with
. The distribution of amounts is slightly right skewed. What normal model describes the average amount spent by 100 randomly selected customers?
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