buted. The sample A simple random sample of size n is drawn from a variance, s,

Question

buted. The sample A simple random sample of size n is drawn from a variance, s, is determined to be 12.7. Complete parts (a) through (c) ulation that is known to be normally distri (a) Construct a 90% confidence interval for of if the sample size, n, is 20 The lower bound is (Round to two decimal places as needed.) The upper bound isRound to two decimal places as needed.) (b) Construct a 90% confidence interval for of if the sample size, n, is 30 The lower bound is (Round to two decimal places as needed.) The upper bound isRound to two decimal places as needed.) How does increasing the sample size affect the width of the interval? ( O O The width does not change The width increases The width decreases (c) Construct a 98% confidence interval for 2 if the sample size, n, is 20 The lower bound is (Round to two decimal places as needed.) The upper bound isRound to two decimal places as needed.) Compare the results with those obtained in part (a). How does increasing the level of confidence affect the confidence interval? OThe width increases O The width decreases ( The width does not change

Explanation / Answer

By the Statistical software output for Variance confidence interval:

a) Lower bound = 8.01

Upper bound = 23.85

b) Lower bound = 8.65

Upper bound = 20.80

The width decreases.

c) Lower bound = 6.67

Upper bound = 31.61

The width increases.

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