## MS Mod 8 Confidence interval for difference in proportions practice...

 Author Message NEAS Supreme Being Group: Administrators Posts: 4.2K, Visits: 1.2K MS Module 8 Confidence interval for difference in proportions practice exam questions(The attached PDF file has better formatting.)The observations and successes for a treatment group and a control group are    treatment    controlobservations    80    101successes    56    67The difference in the probability of success is the probability of success for the treatment group minus the probability of success for the control group.Question 8.1: Sample difference in the probability of successWhat is the sample difference in the probability of success between the two groups?Answer 8.1: 56 / 80 – 67 / 101 = 0.0366Question 8.2: Variance of the differenceWhat is the sample variance of the difference in the probability of success between the two groups?Answer 8.2: (56 / 80 × (1 – 56 / 80) ) / 80 + (67 / 101 × (1 – 67 / 101) ) / 101 = 0.004836Question 8.3: Standard deviation of the differenceWhat is the sample standard deviation of the difference in the probability of success between the two groups?Answer 8.3: 0.0048360.5 = 0.0695Question 8.4: z value for confidence intervalWhat is the z value for the 90% two-sided confidence interval for the difference in the probability of success for the two groups?Answer 8.4: 1.645(the z value for the 90% two-sided confidence interval is the z value for the 95% one-sided test)Question 8.5: Upper bound of confidence intervalWhat is the 90% two-sided confidence interval for the difference in the probability of success for the two groups?A.    0.0446B.    0.0428C.    0.1258D.    0.1510E.    0.2654Answer 8.5: 0.0366 ± 1.645 × 0.0695●    lower bound: 0.0366 – 1.645 × 0.0695 = -0.0777●    upper bound: 0.0366 + 1.645 × 0.0695 = 0.1509 Attachments tud55886 t Junior Member Group: Forum Members Posts: 11, Visits: 151 In Question 8.2: Why we are not using the formula (10.3) in the book pag. 519? NEAS Supreme Being Group: Administrators Posts: 4.2K, Visits: 1.2K +x tud55886 - 10/19/2019 9:11:39 PMIn Question 8.2: Why we are not using the formula (10.3) in the book pag. 519?For a large sample test procedure of proportions when the null hypothesis assumes the probability of success is the same, we use equation 10.4 on page 520.
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