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You are given the sample mean and the population standard deviation. Use this in

ID: 3176041 • Letter: Y

Question

You are given the sample mean and the population standard deviation. Use this information to construct the 90% and 95% confidence intervals for the population mean. Which interval is wider? If convenient, use technology to construct the confidence intervals. A random sample of 38 gas grills has a mean price of $631.80. Assume the population standard deviation is $59.40. The 90% confidence interval is (1, 1). (Round to one decimal place as needed.) The 95% confidence interval is (1, 1). (Round to one decimal place as needed.) Which interval is wider? Choose the correct answer below. The 95% confidence interval The 90% confidence interval

Explanation / Answer

Here it is given mean=631.80 and sd=59.40

Also n=38

so t value for 90 and 95 are 1.6871 and 2.0262 respectively

So for 90% E=t*sd/sqrt(n)=16.26

Hence CI=mean+/-E=631.80+/-16.26=(615.54,648.06)

Similary E for 95%=19.52

Hence CI=(612.28 ,651.32)

Hence we can see 95% CI is wider

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