Question

Assume the conditions necessary for inference are met. Find a 95 ​% confidence interval for the mean audit time. The 95 ​% confidence interval to estimate the mean audit time is from nothing to nothing . ​(Round to two decimal places as​ needed.)

Find a 95%confidence interval for the mean audit time. The 95​% confidence interval to estimate the mean audit time is from nothing to nothing (Round to two decimal places as​ needed.)

2.7

3.6

4.4

3.9

4.9

4.2

2.9

4.2

3.7

4.9

3.7

3.4

3.1

3.9

4.9

Answer 1

∑x = 58.4  

∑x² = 234.3  

n = 15  

Mean, x̅ = Ʃx/n = 58.4/15 = 3.8933

Standard deviation, s = √[(Ʃx² - (Ʃx)²/n)/(n-1)] = √[(234.3-(58.4)²/15)/(15-1)] = 0.7035

95% Confidence interval :  

At α = 0.05 and df = n-1 = 14, two tailed critical value, t-crit = T.INV.2T(0.05, 14) =    2.145

Lower Bound = x̅ - t-crit*s/√n = 3.8933 - 2.145 * 0.7035/√15 = 3.50

Upper Bound = x̅ + t-crit*s/√n = 3.8933 + 2.145 * 0.7035/√15 = 4.28

3.50 < µ < 4.28