Question

The table gives the probability distribution of the number of books sold in a day at a bookstore. What is the probability of 16 or more books being sold on a given day?
number of books sold in a day

0-5

6-10

11-15

16-20

21-25

probability

0.110

0.206

0.464

0.201

?

Answer 1

We are to find the probability of 16 or more books being sold on a given day. So all the categories listing the sale of more than 16 books will be counted for this problem.

From the given table we can see that there are 2 such categories:

1) 16 - 20
2) 21 - 25

To find the probability of 16 or more books sold , we need to add the probability of both these categories. Probability of selling 16 - 20 books is 0.201 and probability of selling 21 - 25 books is unknown. The given distribution is a probability distribution. So sum of probabilities of all categories must be equal to 1. So, the probability of selling 21-25 books is 0.019 only then the probabilities sum up to 1.

Thus, 
The probability that 16 or more books are sold on a give day = 0.201 + 0.019 = 0.220