Source: EconLog

by Pierre Lemieux

“In 1999, Sally Clark, a young British lawyer, was convicted of killing her two newborn babies over a period of two years and she received a life sentence. A pediatrician had testified for the prosecution that the probability that the two boys had died from the Sudden Infant Death Syndrome (SIDS) or ‘crib death’ was about 1 over 73,000,000. This was the only real evidence of the crime. But the probability estimate, which persuaded the jury, was defective. It assumed that the two deaths were statistically independent events, justifying the multiplication of their respective probabilities for both events to happen: 1/8543 × 1/8543 is approximately equal to 1/73,000,000. In reality, however, two SIDS deaths in the same family are not independent events: one such death increases by 10 the medical probability that a second one will happen.” (08/26/24)

https://www.econlib.org/ignoring-probability-theory-is-dangerous/