#### drchrisbrown87

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As per the website riskprediction.org.uk the equation used is:

**Ln R/1-R = -9.065 + (0.1692 x physiological score) + (0.1550 x operative severity score)**

I already have all of the physiological and operative scores.

Extrapolating R from the above equation using

**X**to represent

**-9.065 + (0.1692 x physiological score) + (0.1550 x operative severity score)**

**Ln R/1-R =**

**X**

I have got as far as:

**R = e^[SUP]x[/SUP] /( 1 + e^[SUP]x[/SUP] )**=(-EXP(X)/(EXP(X)-1))

For whatever reason I cannot get the same scores with the exact same data as the above website calculator for P-POSSUM

Is this something to do with rounding errors or is my formula just wrong?! help!

Thanks in advance

Chris