Table 1.
Variables Used | SD | Non-SD | Total |
---|---|---|---|
Presence of WS | a | b | a + b |
Absence of WS | c | d | c + d |
Total | a + c | b + d | a + b + c + d |
Example of the calculation | |||
Sensitivity = a/(a + c) | |||
Specificity = d/(b + d) | |||
PPV = a/(a + b) | |||
NPV = d/(c + d) | |||
Example: For any number of warning signs, a = 31, b = 300, c = 3, d = 366. | |||
For one warning sign only, a = 12, b = 155, c = 22, d = 511 | |||
For two warning signs only, a = 11, b = 105, c = 23, d = 561 |