In a random sample of 60refrigerators, the mean repair cost was $134.00 and the
ID: 2933869 • Letter: I
Question
In a random sample of 60refrigerators, the mean repair cost was $134.00 and the population standard deviation is $15.70 Construct a 95% confidence interval for the population mean repair cost. Interpret the results.
Construct a 95% confidence interval for the population mean repair cost.
The 95% confidence interval is (_,_)(Round to two decimal places as needed.)
Interpret you results. Choose the correct answer below.
A. The confidence interval contains 95% of the mean repair costs.
B. With 95% confidence, it can be said that the confidence interval contains the true mean repair cost.
C. With 95% confidence, it can be said that the confidence interval contains the sample mean repair cost.
Explanation / Answer
A 95% CI is given by :
Mean +/- Z*Sigma/sqrt(n)
where, Z = 1.96
Therefore, 134 +/- 1.96*15.7/sqrt(60) = 130.027 to 137.973
We can interpret it has :
B. With 95% confidence, it can be said that the confidence interval contains the true mean repair cost.
B is right, because confidence level says about the interval in which a true population mean lies within a certain range
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