In Example 1, the number of correct guesses may be 0, 1, 2, 3, 4 or 5.
How likely can a guesser get all 5 questions right? The answer is .001,
or about once in every 1000 tries.
How about the likelihood of getting 2 out of 5 questions right? The
answer is .264, approximately a quarter of the time. The following
**probability distribution table**
gives the likelihood or probability of each possible value of *X*.

You can compute these probabilities yourself by successively substituting
*j*=0, 1, 2, 3, 4 and 5 in the formula

(4.2) |

where and noting that 0!=1. This formula is called the

Example 3 (Con't):10 TV sets were sold in one day. What is the probability that 3 extended warranties were sold? Using Equation 4.3 withn=10,p=.20, andj=3, we get

Exercise:Five percent of videos rented at Campus Video are returned late. If 30 videos were rented during the last hour, what is the probability that

a. 2 will be returned late

b. none will be returned late

Binomial probabilities may also be presented in a cumulative form
.
Here is the *cumulative distribution function* (cdf)
for the binomial distribution with *n*=5 and *p*=1/4.

Do you see how to compute ( 4.4) from ( 4.1)? The TI-83 calculator can compute either the binomial pdf or the binomial cdf (see Sections 4.4.3 and 4.4.4 at the end of this chapter).

Exercise:Five percent of videos rented at Campus Video are returned late. If 30 videos were rented during the last hour, what is the probability that

a. 2 or fewer will be returned late

b. 5 or more will be returned late