Difference between revisions of "Sandbox"

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Breaking News
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Understanding uncertainty: Football crazy
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David Spiegelhalter and Yin-Lam Ng
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Plus Magazine, Issue 52
  
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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Plus Magazine is bublished at Ca
  
<table width="77%" border="1">
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Plus magazine opens a door to the world of maths, with all its beauty and applications, by providing articles from the top mathematicians and science writers on topics as diverse as art, medicine, cosmology and sport. You can read the latest mathematical news on the site every week, subscribe to our fortnightly email newsletter, read our online magazine published four times a year, and browse our archive containing all past issues and news items.
  <tr>
 
    <td width="24%" height="39">Sample</td>
 
    <td width="22%"><p align="center">Reoperations </p>
 
      <p align="center">Needed</p></td>
 
    <td width="25%"><div align="center">Sample Size</div></td>
 
    <td width="29%"><div align="center">Sample Proportion</div></td>
 
  </tr>
 
  <tr>
 
    <td height="42">Outside Normal Hours</td>
 
    <td> <div align="center">28</div></td>
 
    <td> <div align="center">82</div></td>
 
    <td> <p align="center">.3415</p>
 
    <td> <div align="center"></div></td>
 
  </tr>
 
    <td>Within Normal Hours</td>
 
    <td> <div align="center">12</div></td>
 
    <td> <div align="center">70</div></td>
 
    <td> <div align="center">.1714</div></td>
 
  </tr>
 
</table>
 
 
 
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.
 

Revision as of 19:46, 18 September 2009

Understanding uncertainty: Football crazy David Spiegelhalter and Yin-Lam Ng Plus Magazine, Issue 52

Plus Magazine is bublished at Ca

Plus magazine opens a door to the world of maths, with all its beauty and applications, by providing articles from the top mathematicians and science writers on topics as diverse as art, medicine, cosmology and sport. You can read the latest mathematical news on the site every week, subscribe to our fortnightly email newsletter, read our online magazine published four times a year, and browse our archive containing all past issues and news items.