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) |