1. ## ROC plotting

I am a true novice of statistics, so would be grateful of easy explanations, as I am trying to create an ROC curve, and understand how to do it conventionally. However I want to display 3 continuous variables as 1 continuous variable instead on my ROC curve. For example a profile signature of 3 continuous variables (eg. progesterone, oestrogen and testosterone) in unison is associated with diabetes. How do I combine 3 variables together to display on the ROC curve as one profile signiture? I considered doing a mean average of the 3 variables, but the range of the values between the different variables are very large (eg. progesterone= 0.1 mg/ml range, oestrogen= 10,000 mg/ml range, testerone=100mg/ml range), and therefore doesnt really do the variables justice. Is there any other choices I have?

2. ## Re: ROC plotting

I'm not sure what you mean by that. What do you think a ROC curve tells you?

3. ## Re: ROC plotting

I know a program would do it for you (e.g., SAS), but in my mind I cannot conceptualize how to do it solely by hand work. You would plot everypersons sen and 1-spec but what if progesterone is high and testos is low then the next person the progesterone is high and so is testosterone but both have diabetes. You would use a classification table but unsure how you would decide who falls below the cut off.

What I may do is generate the beta coefficients from the logistic model the plug into the model and see if any levels preset themselves.

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