Table 16.1My probability of correctly detecting L toffees: pre-test probability of 25 per cent

Truly L toffeesTruly NOT-L toffeesTotalProbability of a toffee being L
I think that they are L toffees8030110Post-test prob. for a positive test = 80/110 = 73%
I think that they are NOT-L toffees20270290Post-test probability for a negative test = 20/290 = 7%
Total100300400Pre-test probability = 100/400 = 25%

From: Chapter 16, Is this a useful diagnostic test?

Cover of Smart Health Choices
Smart Health Choices: Making Sense of Health Advice.
Irwig L, Irwig J, Trevena L, et al.
London: Hammersmith Press; 2008.
Copyright © 2008, Professor Les Irwig, Judy Irwig, Dr Lyndal Trevena, Melissa Sweet.

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