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Overview :
The discriminant power for a test, also termed the test
effectiveness, is a measure of how well a test distinguishes between affected
and unaffected persons. It is the log of the positive likelihood ratio plus the
log of the negative likelihood ratio, scaled by the standard deviation of the
logistic normal distribution curve (square root of 3 divided by π). Test
effectiveness is interpreted as the standardized distance between the means for
both populations.
discriminant power =
= (SQRT(3) / π) * (LN(X) + LN(Y))
X =
= ((sensitivity) / (1 - (sensitivity)))
Y =
= ((specificity) / (1 - (specificity)))
Interpretation:
• A test with a
discriminant value of 1 is not effective in discriminating between affected and
unaffected individuals.
• A test with a
discriminant value of 3 is effective in discriminating between affected and
unaffected individuals.
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