# QNT561_The_Payment_Time_Case_Week_4.docx - 1 The Payment...

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1The Payment Time CaseWendy KaminskiQNT/561August 14, 2017Chong Ho Yu
295% Confidence Interval EstimateTo construct a 95% confidence interval estimate we will need to have three essential data already computed. The three essential data is the mean, the standard deviation and the sample size. We already know that the standard deviation is 4.2 days. The sample size is 65 and the mean after you average the 65 numbers together is 18.11. After calculating these numbers, we then have calculated the standard error. To get this amount you have to divide the standard deviation (4.2 days) by the square route of the sample size (65). The answer to the equation 4.2/ √ (65) = .52. We then found the margin of error by multiplying .52 (standard error) by 1.96(Z value); which equals 1.02. We are now able to calculate the confidence interval. This is a two part equation. The first is to add the margin of error (1.02) to the mean (18.11); which equals 19.13. We then subtract the two 1.02 - 18.11 which equals 17.09. This means the 95% confidenceinterval estimate is between 17.09 and 19.13.