Thread: probability on phone line

Since they're independent events, P(four consecutive busy)=1/3^4=1/81 Obviously, 1/4>1/81, so answer is B.

Quote: Originally Posted by walt526 Since they're independent events, P(four consecutive busy)=1/3^4=1/81 Obviously, 1/4>1/81, so answer is B. Still not clear. Can you please further explain CB

The joint probability of independent events is simply the product of the individual probabilities. Since each day has a 1/3 chance of a busy signal, the chance of four consecutive days being busy is 1/3*1/3*1/3*1/3=1/81

Quote: Originally Posted by walt526 The joint probability of independent events is simply the product of the individual probabilities. Since each day has a 1/3 chance of a busy signal, the chance of four consecutive days being busy is 1/3*1/3*1/3*1/3=1/81 Ooooh. I misunderstood it at first. But now it's clear. ...