Difference between revisions of "Sandbox"

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<b>Test and CI for Two Proportions </b>
 
<b>Test and CI for Two Proportions </b>
  
Sample  X  (:} N <:Sample p<br>
+
Sample  X  :  N : Sample p<br>
 
1            56  814  0.068796<br>
 
1            56  814  0.068796<br>
 
2            28  813  0.034440<br>
 
2            28  813  0.034440<br>

Revision as of 14:03, 26 September 2009

Flu Shots

The Wall Street Journal of September 24, 2009 reports on a study in the current issue of the New England Journal of Medicine dealing with the efficacy of flu shots during the “2007-2008 flu season.” There were “1952 healthy adults who received either a placebo or one of two [types of] vaccinations,” either a shot or a spray.

“Of the 813 volunteers who received the flu shot, 28 of them or 3.4%, later developed a confirmed case of influenza. In the FluMist group; 56 of the 814 volunteers, or 6.9% developed the flu, while 10.8% of the placebo group had confirmed flu cases.”

Discussion

1. Here is the Minitab output for the comparison between the two forms of vaccination:

Test and CI for Two Proportions

Sample X : N : Sample p
1 56 814 0.068796
2 28 813 0.034440


Difference = p (1) - p (2)
Estimate for difference: 0.0343557
95% CI for difference: (0.0129208, 0.0557907) Test for difference = 0 (vs not = 0): Z = 3.14 P-Value = 0.002

Fisher's exact test: P-Value = 0.002

How does this output support the conclusion that the shot works better than the spray?

2. Because the number of volunteers is 1952 and then total number in the control arms is 1627 (814 + 813), the number of volunteers is 325. Below it’s the Minitab output comparing the controls vs. the placebo:

Test and CI for Two Proportions

Sample X N Sample p
1 35 325 0.107692
2 84 1627 0.051629


Difference = p (1) - p (2)
Estimate for difference: 0.0560635
95% CI for difference: (0.0206880, 0.0914391)
Test for difference = 0 (vs not = 0): Z = 3.86 P-Value = 0.000

Fisher's exact test: P-Value = 0.000

How does this support the conclusion that the vaccinations work better than the placebo?

3. According to the article, the makers of the shot, Sanofi Pasteur, “provided funding for the study” and the lead author “reports receiving lecture fees from the company.” No mention is made of Medimmune Inc., makers of the spray. How does this modify your conclusions?

4. Roughly 5% (84 of 1627) of those who received a vaccination still became confirmed flu victims. Find a friendly librarian to determine how this compares with vaccinations for other diseases such as measles, mumps, rubella, chicken pox and shingles.