Calculating sensitivity and specificity values of a confusion matrix

[CaraJ]

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

[Reeza]

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

[CaraJ]

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).

[Reeza]

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;

[CaraJ]

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.