Question

1.) If you have two treatments that are independent samples and you assume a normal distribution of the data, which test(s) would be appropriate to use? Select all that apply.

		Mann-Whitney U-test
		Paired t-test
		Welch's t-test
		Two-sample t-test
		Sign test 2.)The [x] is used to test a null hypothesis that the mean difference of paired measurements equals a specified value. 3.) To examine the potential effects on the transmission of dengue, Bian et al. (2010) infected mosquitoes from both the WB1 (laboratory created) strain and the original wild strain with dengue. Fourteen days later, the mosquitoes were allowed to feed on an artificial food solution for 90 minutes. Viral titers in the food solution were then measured (in plague feeding units [pfu] per ml. The results are given below. Mosquitoes were tested in groups, and so each data value is an average for the group, measured in pfu/ml. The data have already been log-transformed using log(Y+1), to better visualize the differences. WB1: Wild: 8 11.3 5.9 10.8 4.4 9.4 4.4 6.5 2.4 6.3 0 5.9 0 4.7 0 4.2 Rank the data and use the Mann-Whitney U-test to solve for U2. Round your answer to 1 decimal place 4.) The distribution of body size of chiggers (as measured by weight) is known to be log-normal (that is, size is normally distributed if log transformed). The log-transformed mean weight of 11 female and 9 male chiggers are listed in the table below. Female Male Log-transformed Mean Weight (mg) 25.12 19.29 Standard Deviation 4.12 3.09 Solve for the standard error of the difference between two means. Round your answer to 3 decimal places.

Answer 1

Question 1: Mann-Whitney U test: The Mann-Whitney U test is a nonparametric test that allows two groups or conditions or treatments to be compared without making the assumption that values are normally distributed Paired t-test: A paired t-test is used to compare two population means where you have two samples in which observations in one sample can be paired with observations in the other sample. The assumption of normality is satisfied. Welch's t-test: Mean comparison is the central theme of many classical statistical procedures. Welch's t-test is generally preferred when the variances of two tested means from independent populations are not equal Two sample t-test: it is compare the means of two independent samples and satisfies normality assumption. Sign test: The sign test is a statistical test to compare the sizes of two groups. It is a non-parametric or "distribution free" test, which means the test doesn't assume the data comes from a particular distribution The correct option is Two sample t-test.