Which technique used in Exercise 7 could lead to a biased study? Explain.

Data from Exercises 7

Identify the sampling technique used in each study. Explain your reasoning.

A journalist asks people at a campground about air pollution.

For quality assurance, every tenth machine part is selected from an assembly line and measured for accuracy.

A study on attitudes about smoking is conducted at a college. The students are divided by class (freshman, sophomore, junior, and senior). Then a random sample is selected from each class and interviewed.