A contingency table may arise from an experiment (where one variable is controlled by the experimentor) or a survey (where there is no control over the individuals).
Example (from experiment)
A company that produces and markets videos continuing education programs for the financial industry has traditionally emailed sample videos with previews of the programs to prospective customers. To find whether giving temporary access to the full videos would increase the number of purchases, 40 contacts were randomly selected from the company's mailing list and given access to full videos and another 40 were sent sample videos.
Purchased | Not purchased | |
---|---|---|
Sample video | 6 | 34 |
Full video | 14 | 26 |
Example (from survey)
Urine drug screening was performed on 2537 applicants for career craft positions in the US Postal Service's Boston Management Sectional Center. The contingency table below shows the distribution of test results, split by gender. (Those testing positive for more than one drug were classified under the more serious of the drugs, so each individual only contributed to a single cell in the table.)
Negative | Marijuana | Cocaine | Other drugs | Total | |
---|---|---|---|---|---|
Male | 1465 | 146 | 33 | 28 | 1672 |
Female | 764 | 52 | 22 | 27 | 865 |