5.10 Interactive doping LR

The example above shows that even in cases when the LR supports one proposition over the other, the posterior odds can still be heavily against the favoured proposition being true. The result depends on the base rate and the characteristics of the test that is being applied. In the doping example, the base rate of doping athletes is low and so even a positive test result from a test with 0.95 sensitivity and specificity still results in posterior odds which favour the athlete not doping.

Below is an interactive tool to further explore the doping example. Change the sensitivity and specificity of the test and read the descriptions and calculations for the prior odds, LR, and posterior odds to put their values into context. See if you can find a combination of sensitivity and specificity which results in posterior odds that favour a randomly selected athlete to be doping. More interactive examples can be found in our interactive application.