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Confidence interval and t-distributions

In a random sample of 62 bolts, the mean length was 1.87 inches and the standard deviation was 0.07 inch. Use a normal distribution or a t-distribution to construct a 90% confidence interval or the mean.

Which distribution should be used to construct the 90% confidence interval?
A. Use a normal distribution because the lengths are normally distributed and o is
known
B. Use a t-distribution because the lengths are normally distributed and o is known.
C. Use a t-distribution because n>30.
D. Use a normal distribution because n>30.

The 90% confidence interval is (_____,______)
(round to two decimal places as needed)

Solution Preview

In a random sample of 62 bolts, the mean length was 1.87 inches and the standard deviation was 0.07 inch. Use a normal distribution or a t-distribution to construct a 90% confidence interval or the mean.

Which distribution ...

Solution Summary

The solution determines the confidence interval and t-distributions for bolts. Random sample bolt lengths are determined. Normally distributed interval means are determined.

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