Online sampling is biased because only the people who happen to visit the web site will take the survey.

A radio call-in survey is biased because only people who feel strongly about the topic will respond.

A survey handed to every third person leaving a library is biased because everyone leaving the library was not asked to participate.

Asking for experts to take a survey is biased because they may have particular knowledge of the topic.

{(2,4), (1,2), (0,0), (-1,2), (-2,4)}

{(2,4), (1,1), (0,0), (-1,1), (-2,4)}

{(2,2), (1,1), (0,0), (-1,1), (-2,2)}

{(2,2), (1,1), (0,0), (1,-1), (2,-2)}

favorite stores at which you shop

U.S. Representatives and their home states

sales tax rate in each New York county

opinion of a freshman on the color of Paul’s shirt

27

62

88

90

2.0

2.5

2.8

3.7

the colors of the birds at the city zoo

the shoe size of the zookeepers at the city zoo

the heights of the giraffes at the city zoo

the weights of the monkeys at the city zoo

306

816

4896

5832