One of the features that may suggest a cause-and-effect relationship from an observational study is a “dose-response” relationship.
a. Explain what is meant by a dose-response relationship.
b. Give an example of a possible dose-response relationship.
c. Can a dose-response relationship exist if the explanatory variable is categorical (and not ordinal)? Explain. For Exercises 25 to 29, refer to the news stories in the Appendix and/ or corresponding original source on the companion website. In each case, identify which of the “Reasons for Relationships between Variables” described in Section 11.3 are likely to apply.