The Salk Vaccine Trials of 1954 included a randomized control double blind study in which elementary school
Question:
The Salk Vaccine Trials of 1954 included a randomized control double blind study in which elementary school children of consenting parents were assigned at random to injection with the Salk Vaccine or a placebo. Both treatment and control group were set at 200,000 because the target disease , infantile paralysis (POLIO) was uncommon, but in many cases deadly. The number in the control group ended up to be 199,858 and the number in the treatment group ended up to be 199,944. Dropouts for various reasons in field trials are common for various reasons. At the end of the study there were 142 polio cases in the control group and 56 polio cases in the treatment group. The actual study is more interesting than this because there were degrees of severity of polio cases ranging from mild cold symptons to death (sounds like a virus going around now but less contagious).
a) This study is:
a) Retrospective experiment
b) Retrospective observational study
c) Retrospective experiment
d)prospective experiment
b) Test the hypothesis that the proportion of polio cases is less in the treatment group than in the control group and state your conclusion
c) Find a 95% confidence interval for the difference between the two proportions and report a conclusion based on this interval
d) An alternative method for testing equal proportions is to look at only the 198 children who contacted polio. Each of them had a 50% chance of being assigned to the treatment group or to the control group. If the treatment had no effect then half of these cases should have come from the treatment group and half from the control group. Under the null hypothesis of no difference the sampling distribution of the proportion of the 198 who are in either group has a mean of ½ and if the normal approximation is appropriate N(1/2, Sqrt(p*(1-p)/n). Is the observed proportion of the 198 cases in the control group significantly larger than would be expected under the null hypothesis? (Or another way of thinking about this is: is the observed proportion of the 198 cases in the treatment group less than would be expected under the null hypothesis?) This is a conditional test – conditional on the number getting the disease. It is useful here because the disease probabilities are so small. State a conclusion based on this conditional test.
e) Find the ODDS of getting polio for the control (placebo) group and for the treatment (Salk Vaccine) group
f) Find the one sided p-value for testing the hypothesis that the ODDS of Polio are the same for the placebo and for the Salk Vaccine.
g) Find the Odds Ratio, Give a 95% Confidence interval on the Odds ratio and write a statement interpreting this result.
h) Do you think giving the difference in the proportions between treatment and control (your answer in part c) or the odds ratio(part g) is a better way to understand these results (there is no right answer to this)
The Legal Environment of Business A Critical Thinking Approach
ISBN: 978-0132664844
6th Edition
Authors: Nancy K Kubasek, Bartley A Brennan, M Neil Browne