A. In another study of 300 respondents, researchers asked people how many miles

Question

A. In another study of 300 respondents, researchers asked people how many miles per year they think they drive. The mean “miles per year” in this sample is 10,000. The researchers computed a standard error of 200. [Note: not standard deviation, but they’ve computed the standard error already.] What is the 95% confidence interval that estimates the mean for the population? It would be good to keep notes on how you compute your answer so you can compare it to the answer key. NOTE: For this question, report answers in whole numbers only - no commas or decimals. [HINT: rounding should not be required if you calculate the answer correctly!]

B. Consider the previous question. What would be the z-score you would use to compute the 99% confidence interval? You may find it useful to remind yourself by drawing a bell curve, and shading in the left and right regions of the curve you are interested in when determining what z-score you would use. Then consult your z-table to calculate.

Explanation / Answer

Mean=10000, SE=200

95%CI->[10000-1.96*200,10000+1.96*200]=[9608,10392]

b)Z(99% CI)=2.576

99% CI->[10000-2.576*200,10000+2.576*200]=[9485,10515]

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