Common HIV source in 4 women '80 pc likely'

This article reports a high probability (.7 to .8) that the HIV virus in the women came from the same source. Does the combining of these probabilities increase the belief that the women were infected in the doctor's surgery?

Although it is not possible to determine, without further research, how these probabilities were calculated, they illustrate the use of both "large" and "small" probabilities to support cases. One must be careful in interpreting the context in each case.

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