Parameters:
(1) age: between 29.5 and 80.5 years
(2) body mass index (BMI): between 19.5 and 40.5 kg per meter square
When the nomogram is examined (Cox, Figure 3) it can be seen that the different probability lines are parallel. Each line is of the form:
BMI =
= ((slope) * (age in years)) + (intercept)
If all of the lines are examined, it can be seen that:
(1) the average slope is -1.04
(2) the intercepts for the lines forms a second order curve
If the intercepts for each probability are analyzed in JMP, the following equation is derived:
probability for successful mapping =
= (-0.0118 * ((intercept) ^ 2) + (1.228 * (intercept)) + 64.2
If the line equation for BMI is rearranged:
intercept for a given probability =
= (BMI) + (1.04 * (age in years))
The probability for successful mapping can then be calculated by using this expression for the intercept,
