Question

A ["prospective", OR "retrospective"] cohort study is carried out to investigate the association between occupational arsenic inhalation and neurological exposure and neurological effects among workers in a copper smelter. For the sake of simplicity, let’s assume there are two possible exposure categories: high and low (for example, those working in the smelting process and those working in administration). The exposure was carefully assessed by review of company records which reflected very good exposure monitoring (both air sampling and urine testing). The outcome was based on self-reported information from an interview that asked: “Have you had tingling in your fingers in the last month that lasted more than 30 minutes?” Those that said “yes” were classified as “diseased”, and those that said “no” were the “non-diseased” group. In order to avoid ["information bias", OR "selection bias"]   bias, the company encouraged everyone to participate by telling their workers that they were a concerned employer and wanted to know if there were adverse neurological effects from the potential arsenic exposure in some of the work areas.

The following is the resulting 2 x 2 table:

	Diseased	Not Diseased	Total
High Exposure	60	100	160
Low Exposure	40	350	390
Total	100	450	550

Answer 1