An article titled "Guard Your Kids Against Allergies: Get Them a Pet" (San Luis Obispo Tribune, August 28, 2002) described a study that led researchers to conclude that "babies raised with two or more animals were about half as likely to have allergies by the time they turned six."
a. Do you think this study was an observational study or an experiment? Explain.
b. Describe a potential confounding variable that illustrates why it is unreasonable to conclude that being raised with two or more animals is the cause of the observed lower allergy rate.