Table 5

Everard’s calculations

For purposes of calculation W, SN, SP, and P are expressed as numbers between 0 and 1, rather than as percentages.
What is the null hypothesis?That the DefRay will not be more than 90% sensitive and 70% specific for detecting ankle fractures
What is the lowest sensitivity that is acceptable?95% (call it SN)
What is the lowest specificity that is acceptable?80% (call it SP)
What do you want the confidence intervals to be?5% for sensitivity (Call it W)
How many patients in the study will have the target disorder? (In this case ankle fractures in Egbert’s population of patients)30% (Call it P)