A surveyor wants to know how many shoppers at a mall like to read books. He surveys 100 people coming out of a bookstore at the mall.

Why is the sample biased?

It is unlikely that people who shop in bookstores are interested in surveys.

The surveyor did not sample the entire population at the mall.

There are not enough people in the sample.

People who shop in bookstores are likely to read more books than those who do not.