For a particular office telephone seven telephone calls are

For a particular office telephone, seven telephone calls are randomly received in a week, and these calls are randomly distributed among the seven days. What is the probability that no call will be received on exactly one day?

Solution

Total calls in a week 7

They are randomly distributed among the seven days

P(no call received on one day)

= Prob 7 calls received on other 6 days

Let X be the no of calls received on one day

X can take values as 0 to 7

Each call receiving is independent with p = 1/7.

X is binomial as there are two outcomes.

P(X=0) = 0.3398