Score: 0 of 1 pt 33 of 40 (7 complete) HW Score: 20%, 10 of 50 pts 6.2.28 Questi

Question

Score: 0 of 1 pt 33 of 40 (7 complete) HW Score: 20%, 10 of 50 pts 6.2.28 Question Help (12:15 P In a random sample of 56 bolts, the 80% confidence interval for the mean. e mean length was 1.53 inches and the standard deviation was 0.08 inch. Use a normal distribution or a t-distribution to construct a led Which distribution should be used to construct the 80% confidence interval? A. Use a normal distribution because the lengths are normally distributed and is known B. Use a t-distribution because n230 use a t-distribution because the lengths are normally distributed and o is known. Use a normal distribution because n 2 30 O ce D.

Explanation / Answer

ANSWER: D) Use a normal distribution because n >= 30.

The T-distribution is used when :

i) Population standard deviation is unknown

ii) small sample size ( n <= 30)

In our case, we have the sample standard deviation and not the population standard deviation BUT we have a sample size of n = 56 which is much more than 30 and for this reason alone, we should construct with normal distribution and not T-distribution.

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