Question of the week – Statistics

This table shows study results where MRI results where confirmed by arthroscopy:

In terms of this table (A,B,Cand D) please:

  1. Define sensitivity
  2. Define specificity
  3. Define PPV
  4. DefineNPV


Be able to draw this table and talk examiner through it as you go. Ensure you leave no room for confusing double negatives.

Sensitivity = True Positive/ True Positive + False Negative

Specificity = True Negative/ True negative + False Positive

Positive Predictive Value = True Positives / True Positives + False Positives

Negative Preditive Value = True Negatives / True Negatives + False Negatives

Note: NPV = C/C+D – error on image


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Good Luck!

FRCS Ortho Team


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