Difference between revisions of "Sandbox"

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Breaking News
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The Wall Street Journal of September 8, 2009 reports on a study in the Journal of Bone and Joint Surgery: “The researchers compared the outcomes of patients who underwent surgery between 6 a.m. and 4 p.m. for fractures of the femur or tibia to those who had comparable surgeries for similar fractures outside those normal hours.” 
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<table width="77%" border="1">
 
<table width="77%" border="1">
 
   <tr>  
 
   <tr>  
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     <td>Within Normal Hours</td>
 
     <td>Within Normal Hours</td>
 
     <td> <div align="center">12</div></td>
 
     <td> <div align="center">12</div></td>
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The results are:
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Difference = p (1) - p (2)
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Estimate for difference:  0.170035
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95% CI for difference:  (0.0346494, 0.305420)
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Test for difference = 0 (vs not = 0):  Z = 2.37  P-Value = 0.018
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Fisher's exact test: P-Value = 0.026
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Discussion
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1. Why is the Fisher exact test P-Value (0.026) to be preferred to the other P-Value mentioned (0.018)?
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2. The Wall Street Journal mentioned several caveats “making it difficult to determine the underlying reasons for the after-hours patients’ poor outcomes.”  List a few practical significance hedges to the statistically significant result.
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     <td> <div align="center">70</div></td>
 
     <td> <div align="center">70</div></td>
 
     <td> <div align="center">.1714</div></td>
 
     <td> <div align="center">.1714</div></td>
 
   </tr>
 
   </tr>
 
</table>
 
</table>

Revision as of 13:52, 13 September 2009

Breaking News

The Wall Street Journal of September 8, 2009 reports on a study in the Journal of Bone and Joint Surgery: “The researchers compared the outcomes of patients who underwent surgery between 6 a.m. and 4 p.m. for fractures of the femur or tibia to those who had comparable surgeries for similar fractures outside those normal hours.”

The results are:

Difference = p (1) - p (2) Estimate for difference: 0.170035 95% CI for difference: (0.0346494, 0.305420) Test for difference = 0 (vs not = 0): Z = 2.37 P-Value = 0.018

Fisher's exact test: P-Value = 0.026

Discussion

1. Why is the Fisher exact test P-Value (0.026) to be preferred to the other P-Value mentioned (0.018)?

2. The Wall Street Journal mentioned several caveats “making it difficult to determine the underlying reasons for the after-hours patients’ poor outcomes.” List a few practical significance hedges to the statistically significant result.

Sample

Reoperations

Needed

Sample Size
Sample Proportion
Outside Normal Hours
28
82

..

Within Normal Hours
12
70
.1714