Chapter 2: simulated sensitivity and specificity

We can simulate the sensitivity and specificity of the test at these 4 gestational latencies in the following way:

URNall=HIT+MISS+CR+FA; %size of urn containing all tests

URNhm=HIT+MISS; %urn containing all testees with disease

URNcf=CR+FA; %urn containing all testees without disease

HCR=[0 0]; PN=[0 0]; %simulated numbers of hits/CR and pos/neg results

REPS=40000;

for n=1:REPS,

PNind=1+(randi(URNall)>URNhm); PN(PNind)=PN(PNind)+1;

if PNind==1, HCR(1)=HCR(1)+(randi(URNhm)<=HIT);

else HCR(2)=HCR(2)+(randi(URNcf)<=CR); end, end

S=HCR./PN