a study in which the researcher attempts to understand cause-and-effect relationships without assigning subjects to groups or deciding which treatments each group receives

a controlled study in which the researcher attempts to understand cause-and-effect relationships by assigning subjects to groups and deciding which treatments each group receives

For each situation, choose the most appropriate technique for collecting data.

Compare average class size for math classes and English classes in your high school.

For each situation, choose the most appropriate technique for collecting data.

Estimate the number of students in your school who play video games more than 10 hours per week.

Identify each of the following as an observational study or an experiment.

Compare the grades on a final math test of 25 students who use calculators and 25 students who do not use calculators. The students decide which group they are in.

Identify each of the following as an observational study or an experiment.

Compare voter satisfaction levels between people assigned to use either paper ballots or touch‐ screen machines.

Identify each of the following as an observational study or an experiment.

Determine which brands of orange juice people prefer. The people are randomly chosen at the supermarket and are asked to taste both brands without knowing which brand they are drinking.