Question

Prevalence is 37% . If 100 children present with a sore throat, abut 37 will have strep.  

Sensitivity is 95%. If 100 children with strep take the test, about 95 would get a positive result.  

Specify is 98%. If 100 children without strep take the test about 98 would get a negative result.

PART C  

Prevalence 37%                                      sensitivity 95%                                             specify 98%  

Test Positive	352	13	365
Test Negative	18	617	635
Total	370	630	1000

a) How many have strep?
b) Of those with strep, how many are correctly identified?
c) How many have strep, but are missed in testing?
d) How many do NOT have strep?
e) Of those WITHOUT strep, how many are correctly identified?
f) Now find the number of False Positives.
g) How many TESTED positive?
h) How many TESTED negative?

Answer 1

a) How many have strep?

= 370

b)Of those with strep, how many are correctly identified?

tested positive and have strep = 352

c) How many have strep, but are missed in testing?

tested negative and have strep = 18

d) How many do NOT have strep?

=630

e) Of those WITHOUT strep, how many are correctly identified?

tested negative and have no strep= 617

f) Now find the number of False Positives.
tested positive and have no strep= 13

g) How many TESTED positive?
=365

h) How many TESTED negative?

=635