a) (4 pts) Calculate the sensitivity and specificity of the HPT kit, and explain
ID: 89620 • Letter: A
Question
a) (4 pts) Calculate the sensitivity and specificity of the HPT kit, and explain what these numbers mean.
b) (1 pt) How many false positives were there in the initial screen?
c) (1 pt) How many false negatives were there in the initial screen?
d) (2 pts) Calculate the positive predictive value of the HPT kit, and state what this number means.
e) (2 pts) In general terms, what would happen to the sensitivity and specificity of this test if the cutpoint was increased to 40 mIU?
Pregnant Not Pregnant 314 27 Positive HPT Kit Results 133 Negative 326Explanation / Answer
a) Sensitivity = True positive/True positive+False negative
= 314/314+326=0.490625(sensitivity means how often the test is positive)
Specificity=True negative/True negative+False positive
= 133/133+27=0.83125(specificity means how certain the kit is in telling that person is pregnant)
b) False positive =27
c) False negative=326
d) Positive predictive value=True positive/True positive+False negative
=314/314+27=0.9208 (This value reflect the precision of the kit.)
e) By increasing the cut point specificity will increase as number of false positive will decrease but sensitivity will decrease as number of true positive will also decrease.
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