If the rate of infection for a woman in a single unprotected sexual encounter with an infected man is 0.2%,what is the probability she'll be infected if she has unprotected sex with him 10 times?

Question

Quizplus · Accepted Answer

The probability of not getting infected in a single encounter is 99.8% (100% - 0.2%). For 10 encounters, it's (99.8%)^10 = 98.02% chance of not getting infected, so the chance of getting infected is 1 - 98.02% = 1.98%, which is much higher than 0.2%.

If the Rate of Infection for a Woman in a Single