The amount people who pay for electric service varies quite a bit, but the mean monthly fee is $168 and the standard deviation i
s $34. The distribution is not Normal. Many people pay about $90 in rural areas of the country and about $150 in urban areas of the country, but some pay much more. A sample survey is designed to ask a simple random sample of 1,200 people how much they pay for electric services. Let xbar be the mean amount paid. Part A: What are the mean and standard deviation of the sample distribution of xbar? Show your work and justify your reasoning. (4 points) Part B: What is the shape of the sampling distribution of xbar? Justify your answer. (2 points) Part C: What is the probability that the average electric service paid by the sample of electric service customers will exceed $170? Show your work. (4 points)
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By definition of the derivative,
Let x = score on next test
(85+91+x)/3
90
x94
(85+91+x)/3
x