To test the effectiveness of their Covid719 vaccine, Moderna enrolled 30,000 volunteers and randomly assigned half to receive 2 doses of the vaccine and half to receive 2 doses of a placebo. Neither the volunteers nor those evaluating them knew who was in which group. They found a total of 196 cases of symptomatic Covid that started 14 days or more after the second dose; 185 casE in the placebo group and 11 cases in the vaccine group. a. which best describes this study? 0 Randomized controlled double blind study 0 Observational study with historical controls 0 Nonrandomized study with a placebo O Nonrandomized controlled double blind study O Randomized controlled study with a placebo mes om b. which of the following are possible confounders 0 Flu, it's difcult to distinguish u symptoms from Covid symptoms. 0 Both are possible confounders 0 Age, older people are more likely to experience symptoms and more likely to report them. Q Neither are possible oonfounders Submit mower Tries 0.199 c. To test the null hypothesis that there's no diFferenoe between the vaccine and the placebo in preventing Covid, do a 1-sample 2 test. I. Assuming the null to be true, how many of the 196 cases would you expect to come from the vaccine group? S (answer with a number, not a percent) Submit mower Tries 0/99 Ii. Calculate the SE of that case number. I: (answer with a number, not a percent, and round it to 2 decimal places.) Submit Answer Tries 0/99 (Hint: Each of the 196 cases has a 50750 chance of coming from the vaccine or the placebo group so the box model is the same as for ipping a fair ooin 196 times and counting the number of heads) III. 2 statistic = S (round to 2 decimal places) Submit Anew Tries 0/99 iv. p-value is