Answer to Question #203078 in Statistics and Probability for jerzy

Question

in a viral pool test it is known that in a group of 5 people, exactly one will test positive. if they are tested one by one in a random order for confirmation what is the probability the only two test are needed

Answer 1

The first occurrence of success requires 2 trials

$$P=(1-\dfrac{1}{5})(\dfrac{1}{5-1})=\dfrac{1}{5}$$