STAT 2332.001 (Introductory Statistics for Life Sciences) Fall 2017 Quiz 6 (Test Form A) NOTE: Select the best answer and record it on the scantron form. No credit will be given if an answer is not recorded properly on the scantron form. Each question is worth 10 points. 1. A study examined gallbladder function by measuring the gallbladder ejection fraction (GBEF) before and after fundoplication - a surgery used to stop stomach contents from flowing back into the esophagus - in 12 patients with acid reflux disease. Following are the summary statistics for GBEF before and after fundoplication and their differences. before (x) after (y) Difference d=y-x Mean 39 57 18 SD 30 28 33 To test whether fundoplication increases average GBEF, the appropriate null and alternative hypotheses are (A versus. (B) versus. (C) versus. (D versus. 2. (Continuation) The appropriate test statistic is (A) (B) (C) (D) 3. (Continuation) The distribution of the above test statistic under H0 is (A) N(0,1) (B) , where is Satterthwaites degree of freedom (C) t11 (D) t38 4. Is Wheaties a power breakfast? A study is conducted in an elementary statistics class with 499 and 249 students randomized to the treatment (Wheaties) and control (Sugar Pops) groups, respectively after the midterm. Final scores averaged 66 for the treatment group with SD of 21. For the control group, mean and SD were 59 and 20, respectively. An appropriate test statistic and its distribution under H0 is (A) , , where is Satterthwaites degree of freedom (B) , (C) , where = 499+249-2(D) 5. One study of grand juries in Alameda County, California compared the demographic characteristics of jurors with the general population to see if the jury panel were representative. The results for age are shown below. The investigators wanted to know whether these 66 jurors were selected at random from the population of Alameda County. Age 21 to 40 41 - 50 51 - 60 >60 Total County-wide percentage 42 23 16 19 100 Observed jurors 5 9 19 33 66 What is the null hypothesis for this test? (A) The jurors for the four age groups (in order) are selected with probabilities 42%, 23%, 16%, and 19%. (B) The jurors for the four age groups (in order) are selected with probabilities 5%, 9%, 19%, and 33%. (C) The jurors for the four age groups (in order) are not selected with probabilities 42%, 23%, 16%, and 19%. (D) The jurors for the four age groups (in order) are not selected with probabilities 25%, 25%, 25%, and 25%. 6. (Continuation) If these 66 jurors were selected at random from the population of Alameda County, how many jurors do we expect with age > 60? (A) 0.25*66 (B) 0.19*66 (C) 66/100 (D) 0.19/66 7. (Continuation) What test statistic can be used to investigate this question? (A) Two-sample t-test (B) Two-sample z-test (C) Chi-square goodness of fit test (D) Paired t-test 8. (Continuation) Suppose the test statistic value is calculated to be 61. What is our conclusion at 5% level of significance? (The 95%-percentile of – distribution is 7.82) (A) We conclude that the jurors are selected at random because 61 is not an extreme value. (B) We conclude that the jurors are not selected at random because 61 is not an extreme value. (C) We conclude that the jurors are selected at random because 61 is an extreme value. (D) We conclude that the jurors are not selected at random because 61 is an extreme