Meanwhile, in the second week of November 1972, a physician in Feelgood, Idaho, contacted the Idaho State Department of Health by telephone to report a case of shigellosis infection in a young woman who was from Lilyville, Idaho. The young woman/patient lived in an apartment across the street from Lovely Middle School. The young woman shared a common water supply with the school. Several guests who attended a gathering at her apartment on November 4 had experienced gastrointestinal illness.
Similar illnesses were also reported among members of the local Liberty High School boys' basketball team. Another high school boys' basketball team from the neighboring town also reported gastrointestinal illnesses. The two teams had played a scrimmage at Lovely Middle School’s gym on November 15.
Upon investigation, the team realized that the water supplies for Lovely Middle School and the private apartment all came from wells on the school property.
Investigators decided to conduct a more comprehensive survey, including everyone at the school (292), the guests of the apartment gathering (12), and all players, coaches and spectators on the basketball teams that scrimmaged at Lovely Middle School (58).
What questions would you include on this survey? Which questions will you include that would help with bias and/or confounding of your study?