Question

You want to know the brand of jeans worn most often by people 20 to 30 years old.
Which of the following surveys is biased?
surveying people 20 to 30 years old at a store that sells one brand of jeans
surveying people 20 to 30 years old at a store that sells only jeans
surveying everyone at a store that sells only jeans

Answer 1

If you survey people at a store that only sells one brand of jeans, what brand of jeans do you think the people shopping there will wear most often? :P

Answer 2

The first choice is completely biased