Exercises 5–9: random selection and random assignment
take another look at the two studies described above. study a (the dog food study) is an experiment, while study b (text messages) is an observational study. the term random sample
implies that a sample was randomly selected from a population. the terms random selection and random assignment have very different meanings.
random selection refers to randomly selecting a sample from a population. random selection allows generalization to a population and is used in well-designed observational studies.
sometimes, but not always, the subjects in an experiment are randomly selected.
random assignment refers to randomly assigning the subjects in an experiment to treatments. random assignment allows for cause-and-effect conclusions and is used in
well-designed experiments.
in study b, the data were collected from two random samples of students.
5. can the results of the survey be generalized to all ninth-grade and all eleventh-grade students at the school? why or why not? discuss the answer with your partner.