Download Statistics Practice Test Results and Problems Solving and more Exams Biostatistics in PDF only on Docsity! Name: _____________________________ 1 Practice Test 2 - Results Quiz Section (10 Points) a) The distance between canine tooth and molar for 35 wolf upper jaws was measured. The average of the left and right sides of the jaw of an individual wolf were used to calculate a 95% CI for the mean. Thus a total of 70 measurements were made. Could we use n=70 to calculate a 95% CI ? No, using n=70 would assume that the left distance was independent from the right distance on the same animal, which is not true. b) What test do you use to test if the variances of two normally distributed samples are equal or not? F Test c) After you calculate a 95% confidence interval for your sample from population x, you find out that it does not include the mean of population y. What can you conclude if your goal is to compare the two population means? That the means are significantly different d) The power of a test is defined as Pr(reject H0|H0 is false) e) True or False: A 99% CI is wider than the corresponding 95% interval: True f) True or False: Use the non-parametric Sign Test for independent samples: False g) You know that the proportion of a disease in the population is 2%. You calculate a proportion of 4% in your target population using a sample size of 20. What test do you use to compare these proportions? Binomial 1 sample test – Exact method h) True or False: If p<, you accept H1: True i) The brook trout is native to eastern North America, but was introduced to streams in the West for sport fishing. The native Chinook salmon was released in six streams where brook trout was present and in six without the brook trout. The proportion of surviving Chinook Salmon was recorded each time. Although this is about proportions a binomial test is not appropriate here as each stream is the independent sample unit. Which parametric test should we use to prove that the proportions of Chinook surviving is different between streams with and without brook trout? A two independent samples t-test j) State the two possible alternative hypothesis of a 1 sample 1-sided t-test. Either H1:< 0 or H1: >0 Name: _____________________________ 2 Problems (20 points) 1. (9 Points) The data in the table below are measurements from a group of 10 normal males and 11 males with left-heart disease taken at autopsy at a particular hospital. Measurements were made on several variables at that time, and the table presents the measurements on total heart weight (THW). Left-Heart Disease Normal Males ID THW ID THW 1 450 1 245 2 760 2 350 3 325 3 340 4 495 4 300 5 285 5 310 6 450 6 270 7 460 7 300 8 375 8 360 9 310 9 405 10 615 10 290 11 425 a. Test for a significant difference in mean THW between the left-heart disease and normal groups. b. Suppose normality is not assumed, what non-parametric test can be used to compare THW between the left-heart disease groups and normal groups. Wilcoxon Rank Sum test for independent samples
