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#1
07-15-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,867 Threads: 149 Thanked 2,087 Times in 1,047 Posts Reputation: 2107
p value for testing the hypothesis of equal means

Measurements on babies of mothers who used marijuana during pregnancy were compared to measurements on babies of mothers who did not. The sample mean head circumference was larger in the group who were not exposed to marijuana and the 95% confidence interval for the difference in mean circumference between the 2 groups was .61 to 1.19 cm. What can be said about the (2-sided) p value for testing the hypothesis of equal means?

(a) The p value is greater than .05
(b) The p value is equal to .05
(c) The p value is less than .05
(d) The p value is 0
(e) Cannot be determined from the information given.

#2
07-15-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 646 Threads: 52 Thanked 761 Times in 256 Posts Reputation: 772

(a) The p value is greater than .05

because the test is not significant... cos the CI includes the value of 1
#3
07-16-2012
 USMLE Forums Scout Steps History: CS Only Posts: 35 Threads: 3 Thanked 28 Times in 17 Posts Reputation: 38

@mbbs2010

I think what you are implying applies for relative risk.

As far as I remember, when the case involved RR, CI should not include 1
& when the case involved mean difference, then CI should not include 0
for the studies to have any statistical significance.

Correct me if I'm mistaken.

Thanks for posting the question.
#4
07-16-2012
 USMLE Forums Master Steps History: --- Posts: 1,365 Threads: 648 Thanked 585 Times in 354 Posts Reputation: 595

Quote:
 Originally Posted by Novobiocin Measurements on babies of mothers who used marijuana during pregnancy were compared to measurements on babies of mothers who did not. The sample mean head circumference was larger in the group who were not exposed to marijuana and the 95% confidence interval for the difference in mean circumference between the 2 groups was .61 to 1.19 cm. What can be said about the (2-sided) p value for testing the hypothesis of equal means? (a) The p value is greater than .05 (b) The p value is equal to .05 (c) The p value is less than .05 (d) The p value is 0 (e) Cannot be determined from the information given.

 Tags Biostatistics-Epidemiology, Step-2-Questions

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