In his Final exam a Professor permits the use of PCs on the

In his Final exam, a Professor permits the use of PCs on the condition that Wi-Fi is turned off. He has known that 1 out of 15 students will disobey his rule, therefore he does a random check. Find the probability that the first student to disobey (turned on Wi-Fi) was found after 13 students were checked. 0.26 0.29 0.32 0.68

Solution

In geometric distribution,

P(x>n) = (1-p)^n

here, n = 13, p = 1/11, hence,

P(x>13) = (1-1/11)^13 = 0.28966438 = 0.29 [ANSWER, B]