Please select the best choice and leave a brief explanation as to why that is.

21. When the population variances are unknown and are not equal in a hypothesis test for two population means, the test to be performed is also known as A. Paired t-test. B. Pooled t-test. C. Welch two sample t-test D. Two-sample z-test. 22. In testing a hypothesis about two population means, if the t distribution is used, which of the following assumptions is required? A. Both populations from which the samples are to be taken are normally distributed. B. The standard deviations of the populations are not the same. C. The means of the populations are the same. D. The sample sizes are equal. 23. An analyst wishes to determine if there is a significant difference between two population means. A sample of 10 items from population 1 yields a mean of 178 with a standard deviation of 20. A sample of 12 items from population 2 yields a mean of 200 with a standard deviation of 25. Assuming equal population variances, what is the computed test statistic value? A. -2.2926 B. -2.2451 C. 2.5623 D. 2.7512 24. When testing for the difference between the means of two related populations, the usual null hypothesis for the test is A. The difference between the two population means is equal to 1. B. The difference between the two population means is greater than 0. C. The difference between the two population means is equal to 0. D. The difference between the two population means is greater than 1. 25. The Analysis of Variance (ANOVA) is a statistical procedure of comparing the ______ of more than two populations. A. Means B. Variances C. Medians D. Standard Deviations 26. A teacher wanted to determine whether there was a significant difference in the mean daily hours of study for students living in four different dormitories. She randomly selects 50 students from each of the four dormitories. What is the null hypothesis for this situation? A. The mean daily hours of study is 3 hours for each dormitory. B. The mean daily hours of study is not the same for each dormitory. C. The mean daily hours of study is different for each of the 200 students in the sample. D. The mean daily hours of study is the same for all four dormitories. For #27 and #28: A study compared the grade point average (GPA) for students who were divided by 6 locations where they usually sat during lectures (i.e. left or right front, left or right center, left or right rear). A total sample size of 12 students was studied (2 students from each section) using one-way Analysis of Variance. 27. The Error Sum of Squares (SSE) is 50. What is the Mean Square Error (MSE)? A. 4.17 B. 8.33 C. 10.00 D. 12.00 28. The Sum of Squares Treatment or Among Groups (SSA) is 60. What is the Mean Square Among groups (MSA)? A. 10 B. 12 C. 30 D. 60 29. When the One-Way Analysis of Variance (ANOVA) result is significant, that is, the null hypothesis will be rejected, a follow-up test must be performed to determine which particular pairs of groups significantly differ. The follow-up test procedure is called a A. Multiple two-sample t-test B. Multiple two-sample z-test C. Post-hoc analysis D. Tukey's method 30. The following are assumptions underlying the use of ANOVA except A. The samples that constitute the groups should be independent. B. The variances of the subgroups should be homogeneous. C. The individuals in the various subgroups should be selected on the basis of random sampling from normally distributed populations. D. The data obtained for each sample should be approximately normal.