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#1
06-18-2015
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Help!!! Question from NBME 7

Plz help me figure out the ans to this biostat question from nbme 7._

Two programs for treatment of patients with newly detected hypercholestrolemia were tried in a community. Program A was used in one district of community and program B was used in another. After four years, 40% of 110 patients on Program A and 53% of the 95 patients on Program B had been successfully treated for hypercholestrolemia. The p value for the difference was 0.3. Based on these data, the health officials decide not to change to Program B in the first district. Which of the following best explains this decision?

A. They attributed the difference in success rates to chance alone

B. They distinguished between statistical significance and clinical significance

C. They felt the power was too high to justify a decision in favour of Program B

D. They felt the p value was too small to justify a decision in favour of Program B.

#2
06-18-2015
 USMLE Forums Veteran Steps History: Not yet Posts: 207 Threads: 19 Thanked 52 Times in 45 Posts Reputation: 62

Quote:
 Originally Posted by samusmle33 Plz help me figure out the ans to this biostat question from nbme 7._ Two programs for treatment of patients with newly detected hypercholestrolemia were tried in a community. Program A was used in one district of community and program B was used in another. After four years, 40% of 110 patients on Program A and 53% of the 95 patients on Program B had been successfully treated for hypercholestrolemia. The p value for the difference was 0.3. Based on these data, the health officials decide not to change to Program B in the first district. Which of the following best explains this decision? A. They attributed the difference in success rates to chance alone B. They distinguished between statistical significance and clinical significance C. They felt the power was too high to justify a decision in favour of Program B D. They felt the p value was too small to justify a decision in favour of Program B.
c. If you increase p value then you have a greater power. and less chance to conduct type 2 error. this study has a high p value and thats why their power was great.
#3
06-18-2015
 USMLE Forums Scout Steps History: 1+CK+CS Posts: 53 Threads: 7 Thanked 18 Times in 13 Posts Reputation: 28

Quote:
 Originally Posted by samusmle33 Plz help me figure out the ans to this biostat question from nbme 7._ Two programs for treatment of patients with newly detected hypercholestrolemia were tried in a community. Program A was used in one district of community and program B was used in another. After four years, 40% of 110 patients on Program A and 53% of the 95 patients on Program B had been successfully treated for hypercholestrolemia. The p value for the difference was 0.3. Based on these data, the health officials decide not to change to Program B in the first district. Which of the following best explains this decision? A. They attributed the difference in success rates to chance alone B. They distinguished between statistical significance and clinical significance C. They felt the power was too high to justify a decision in favour of Program B D. They felt the p value was too small to justify a decision in favour of Program B.

the standard P value is mostly <0.05 (source FA2014 pg57)

so, anything below < 0.05 = null hypothesis is rejected i.e the chances that the relation between exposure and outcome occured by chance.

and

anything above 0.05(which is in this question,p value is 0.3, well above 0.05) it will make us to not to reject null hypothesis(Ho).

so the option C is saying that the power is too high, whch is correct, 0.3 is higher than 0.05, so null hypothesis cant be rejected meaning program B becomes successful but there is a 30%(0.3) chance that it occured just by chance, whereas 5%(0.05) value was required, thats why we cant make a decision in favor of program B because p value is too high.

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