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chi squared

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The chi squared test is used to compare characteristics of more than two groups (t test would be an appropriate test for 2 characteristics). Using the tables of chi squared will gives the probability of features being due to chance.

The Technique:

  • deal in numbers, not percentages or proportions
  • produce an expected result - total up the results and divide by the number of results
  • Chi squared is equal to the sum of the values of:


( Observed number - Expected number) squared


expected number


(Squaring copes with the problem of negative results).

In the tables need then to allow for degrees of freedom (see degrees of freedom)


General Practice Notebook
General Practice Notebook
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