Referenced from lesson Threats to Validity
Data scientists conducted a study of 15,000 people living in Alaska and New Mexico. They wanted to find out if people in colder climates spent more money on footwear. They discovered that Alaskans spent an average of $150 per year on shoes, whereas New Mexicans spent an average of $45 per year.
Before publishing their findings, the data scientists have asked you to review their claim. In the space below, indicate possible threats to validity faced by this study.
These materials were developed partly through support of the National Science Foundation,
(awards 1042210, 1535276, 1648684, and 1738598). 
Bootstrap:Data Science by Emmanuel Schanzer, Nancy Pfenning, Emma Youndtsmith, Jennifer Poole, Shriram Krishnamurthi, Joe Politz, Ben Lerner, Flannery Denny, and Dorai Sitaram with help from Eric Allatta and Joy Straub
is licensed under a
Creative Commons 4.0 Unported License.
Based on a work at www.BootstrapWorld.org.
Permissions beyond the scope of this license may be available by contacting
schanzer@BootstrapWorld.org.