Finding the optimal decision threshold

Find the optimal decision threshold using information on the relative costs of making correct and incorrect decisions.

1. Activate the analysis report worksheet.
2. On the Analyse-it ribbon tab, in the Diagnostic Accuracy group, click Find Optimal.
   The analysis task pane Decision panel opens.
3. If the sample does not represent the prevalence of the condition in the target population, then, in the Prior probability edit box, type the Prevalence of the condition in the target population.
4. In the TP, FP, TN, FN edit boxes, enter the cost of each type of decision.

   The cost depends on the difference in costs between FPs and TNs relative to the difference in costs between FNs and TPs. Therefore, the costs can be expressed in any unit and need not be purely financial costs. The default costs are equal.

5. If you want a plot of the cost for each possible decision threshold:
   1. On the Analyse-it ribbon tab, in the Diagnostic Accuracy group, click Decision Threshold.
      The analysis task pane Decision panel opens.
   2. In the Plot drop-down list, select Cost.
6. Click Recalculate.