Statistical Error when CI is -2 to 12% - USMLE Forums
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  #1  
Old 08-15-2011
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Stats Statistical Error when CI is -2 to 12%

A young hand surgeon compares functional outcomes in rheumatoid arthritis patients who undergo silicone metacarpophalangeal joint arthroplasty versus patients who undergo standard medical therapy. He finds that mean grip strength is increased by 8% (95% CI: -2% to 12%) in the operative group. Based on these results, he concludes that silicone metacarpophalangeal joint arthroplasty is the better treatment. What type of error has he committed in drawing this conclusion?
A. β-error
B. Type II Error
C. Inadequately powered study
D. Type 1 Error
E. Null Hypothesis error
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Old 08-15-2011
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Default D) Type I error

Type I error ---->there is a difference when there is actually none
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Old 08-16-2011
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The correct answer is D.
The confidence interval includes 0, meaning that the null hypothesis (no difference between operative and nonoperative patients) cannot be rejected. Because this researcherís conclusion incorrectly accepts the alternative hypothesis (H1), he has committed a Type 1 error.
A Type II error would involve failing to reject the H0 (i.e., there is a difference but the researcher didnít find it).
We arenít given any information as to the sample & population sizes, and therefore cannot make any determination regarding whether or not the study was adequately powered.
"Null hypothesis error" is a nonsensical answer choice, as is β-error.
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Old 08-30-2011
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i think its not counted on the bases of 0 but counted weather 1 is included in CF or not.......
if 1 is not included - statistically significance
if 1 is included - not significant
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Old 08-30-2011
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Quote:
Originally Posted by dinosaur108 View Post
i think its not counted on the bases of 0 but counted weather 1 is included in CF or not.......
if 1 is not included - statistically significance
if 1 is included - not significant
We are talking about % here...so, if the x%CI include the zero value = we fail to reject. (the same is true when we're using mean or median values within a CI).

If we were working with RR or OR, then the magic number would be 1.
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