STAT 200 FINAL EXAM A

STAT 200 FINAL EXAM 1. True or False. Justify for full credit. (a) If the variance of a data set is zero, then all the observations in this data set are zero. No, all the observations will be same but it is not necessary that all the observations will be zero, because if all the observations are same even then the variance will be zero. (b) If P(A) = 0.4 , P(B) = 0.5, and A and B are disjoint, then P(A AND B) = 0.9. No, because if A and B are disjoint then P(A AND B) = 0. (c) Assume X follows a continuous distribution which is symmetric about 0. If , then . Yes, P(X<-3) will be less than 0.3 because the value will be towards negative side. (d) A 95% confidence interval is wider than a 90% confidence interval of the same parameter. Yes, a 95% confidence interval is wider than a 90% confidence interval of the same parameter because increasing the confidence limit we increases the acceptance region and reduces the rejection region. (e) In a right-tailed test, the value of the test statistic is 1.5. If we know the test statistic follows a Student’s t-distribution with P(T < 1.5) = 0.96, then we fail to reject the null hypothesis at 0.05 level of significance . No, we will not be able to reject the null hypothesis as we reject the null hypothesis is test statistic is greater than the tabulated value of t.   Refer to the following frequency distribution for Questions 2, 3, 4, and 5. Show all work. Just the answer, without supporting work, will receive no credit. The frequency distribution below shows the distribution for checkout time (in minutes) in UMUC MiniMart between 3:00 and 4:00 PM on a Friday afternoon. Checkout Time (in minutes) Frequency Relative Frequency 1.0 - 1.9 3 2.0 - 2.9 12 3.0 - 3.9 0.20