EXAMPLE 2 The Inconvenient Truth About Convenience Samples

Going to the mall, standing by a particular entrance, and surveying as many of the people walking through that entrance as you can seems like a fast, convenient way of finding out Americans’ opinions. But people at malls tend to be more prosperous than typical Americans. They are also more likely to be teenagers or retired. The kinds of stores that are near the particular entrance you are standing by could affect the type of people you might more readily encounter. Also, when we decide which people to approach, we may tend (even unconsciously) to avoid poorly dressed or tough-looking individuals. in short, our shopping mall interviews will result in a sample that is not representative of the entire population because we underrepresent certain types of people. For that matter, we also are underrepresenting those Americans who rarely go to malls in the first place.

In your classroom, your professor may try to “sample” the understanding the class has about a topic by simply calling on the nearest two students in the front row. If students who sit near the front have higher levels of preparation, interest, and engagement, the professor will overestimate how well the class as a whole understands the material.