topic Re: Calculating sensitivity and specificity values of a confusion matrix in SAS Programming

Calculating sensitivity and specificity values of a confusion matrix

CaraJ — Wed, 06 Feb 2013 21:53:01 GMT

Hi Everyone, I am interested in learning how to write up SAS code to calculate sensitivity and specificity in my confusion matrix (5X5 table) below. Any help would be greatly appreciated .

Program

Syndrome Diarrheal-toxin EC Salmonella Viral Vomiting-toxin

Diarrheal-toxin 50 1 0 2 0

EC 0 25 8 0 0

Salmonella 1 20 252 6 1

Viral 4 0 0 786 39

Vomiting-toxin 2 0 0 0 41

Thank you in advance

Re: Calculating sensitivity and specificity values of a confusion matrix

Reeza — Wed, 06 Feb 2013 21:55:02 GMT

How are you defining specificity and sensitivity in your particular case?

Re: Calculating sensitivity and specificity values of a confusion matrix

CaraJ — Wed, 06 Feb 2013 22:02:58 GMT

Hi Reeza, sorry I am defining mine as those syndrome outbreaks that are correctly classified in their respective program. For example, I calculate the sensitivity of diarrheal-toxin manually to be 94.3% (50/53).

Re: Calculating sensitivity and specificity values of a confusion matrix

Reeza — Wed, 06 Feb 2013 22:32:54 GMT

I don't recall specificity either (and don't feel like looking it up) but the general idea for sensitivity is simple enough.

data want;

set have;

array cause(5) diarrheal ec salmonella viral vomit;

total=sum(of cause(*));

sensitivity=cause(_N_)/total;

run;

Re: Calculating sensitivity and specificity values of a confusion matrix

CaraJ — Wed, 06 Feb 2013 22:39:30 GMT

Thank you sorry. I should have fully place the definitions up-my apologies but specificity is the probability of the syndromal outbreaks negative for a particular program given that it is not correctly classifed.