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I'm conducting a retrospective study to assess the efficacy of a new test for predicting sudden cardiac death (SCD). I also want to compare the accuracy of my new predictor with that of a conventional predictor. I'm not a statistician, so I would very much appreciate it if any of you experts can confirm that I'm in the right direction w.r.t the statistical tests I need to use.

  1. I'm planning to use Fisher's exact test to see if my new predictor is associated with occurrence of SCD. That is, I will divide my sample of patients into two groups, one group in which patients died of SCD, and the other in which no one died of SCD, and I will compare between the two groups the proportion of patients in which my predictor was positive. Am I using the Fisher's test appropriately here?

  2. I'm planning to use McNemar's test to compare the accuracy of my new predictor with that of the conventional predictor. That is, I will have a 2x2 contingency table with the following entries:

    Top left cell: # patients in which both predictors accurately determined whether or not they died of SCD. Top right cell: # patients in which my predictor was accurate but the conventional predictor was not. Bottom left cell: # patients in which my predictor was not accurate but the conventional predictor was. Bottom right cell: # patients in which both predictors were inaccurate.

Is my use of McNemar's test correct?

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  • $\begingroup$ I don't see a problem in your approach. Don't forget the descriptive part though. $\endgroup$ – Michael M Jul 16 '14 at 14:38
  • $\begingroup$ Are these predictors truly binary or are you dichotomizing them? $\endgroup$ – gung Jul 16 '14 at 14:44
  • $\begingroup$ Yes, these predictors are truly binary. $\endgroup$ – Fijoy Vadakkumpadan Jul 16 '14 at 14:45

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