In a random sample of 60 refrigerators, the mean repair cost was exist116.00 and

Question

In a random sample of 60 refrigerators, the mean repair cost was exist116.00 and the population standard deviation is exist16.50. Construct a 90% confidence interval for the population mean Interpret the results. Construct a 90% confidence interval for the population mean repair cost. The 90%confidence interval is (, ). (Round to two decimal places as needed.) Interpret you results. Choose the correct answer below. With 90%confidence, it can be said that the confidence interval contains the true mean repair cost. With 90% confidence, it can be said that the confidence interval contains the sample mean repair cost. The confidence interval contains 90% of the mean repair costs.

Explanation / Answer

We dont know the population mean.

we know the population standard deviation.

we know the sample mean.

now, the formula for Confidence Interval of population mean is given by :

CI = x ± Z/2× (/n)

where
x=sample mean

alpha=level of significance

sigma=standard deviation.

n=sample size

so, here , putting the values

x=116

n=60

sigma=16.50

alpha=0.9

the 90% CI is : (112.485, 119.515)

The cnfidence interval is supposed to give us an interval estimate within which our unknown parameter, the true mean, lies.

So, option A is right.

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