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Old 11-17-2012
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Stats biostat problem regarding confidence intervals

Two experimental drugs, drug X and drug Y, are being evaluated for treatment of congestive heart failure. Patients receiving drug X have a cardiac index of 2.5 L/m2 with 95% confidence interval of 1.5 to 3.5. Patients receiving drug Y have a cardiac index of 1.7/m2 with a 95% confidence interval of 0.7 to 2.7. A test of the significance of difference shows a p value of 0.1. Which of the following is the likelihood that the difference in mea cardiac index of patients receiving drug X and drug Y is due to chance?

a. 0%
b. 2.5%
c. 5%
d. 7.5%
e. 10%
f. 66.7%
g. 95%
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Old 11-17-2012
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10% (p=0.1)
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Old 11-17-2012
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Default my answer :)

e. 10% = p value
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Old 11-17-2012
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Is this question asking about likely hood of type 2 error???
If yes, then if p value is above 0.05 then type to error is not equal to p value.
I think i am getting lost here. any insight??
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Old 11-17-2012
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There is an overlap of the confidence intervals between the two drugs. So statistically there is no significant difference in the efficiency of the two drugs.

Therefore I would go for answer g (95%) (its the maximum likelihood that the difference is due to chance, from the given options). I would go for 100% if it was listed as one of the options.

I don't have the correct answer. Just my chain-of-thoughts. What do you think?
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Old 11-17-2012
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Quote:
Originally Posted by wertheworld11 View Post
There is an overlap of the confidence intervals between the two drugs. So statistically there is no significant difference in the efficiency of the two drugs.

Therefore I would go for answer g (95%) (its the maximum likelihood that the difference is due to chance, from the given options). I would go for 100% if it was listed as one of the options.

I don't have the correct answer. Just my chain-of-thoughts. What do you think?
Answer is E . I have answer sheet
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Old 11-18-2012
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the problem is that I saw the answer sheet too like you but didn't agree with the answer. That is why I posted the question so that someone could explain the answer giving the appropriate reason. I still think it should be 95%. Anyone here with good knowledge in biostat who can explain?
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Old 11-18-2012
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Quote:
Originally Posted by wertheworld11 View Post
the problem is that I saw the answer sheet too like you but didn't agree with the answer. That is why I posted the question so that someone could explain the answer giving the appropriate reason. I still think it should be 95%. Anyone here with good knowledge in biostat who can explain?
the most important/useful sentence in the whole stem is:
"A test of the significance of difference shows a p value of 0.1."

Then, they ask: "Which of the following is the likelihood that the difference in mean cardiac index of patients receiving drug X and drug Y is due to chance?" - which is basically a textbook definition of type I error (alpha).Since alpha = p value, the answer is
e. 10%
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DrSK (11-18-2012), koolkiller88 (11-18-2012)



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