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Tabulate positive test results in one column and negative test results in the other.įor data from prospective and experimental studies, the top row usually represents exposure to a risk factor or treatment, and the bottom row is for controls. One sample has the disease or condition you are testing for, the other does not. Contingency tables also assess the accuracy of a diagnostic test.The rows represent alternative treatments, and the columns tabulate alternative outcomes. Contingency tables can also tabulate the results of some basic science experiments. Enter the number with leukemia in one column, and the number without leukemia in the other column. After a suitable period of time, assess whether each animal has leukemia. Half are exposed to EMF, while half are not.

For example, you could perform a study of the EMF/leukemia link with animals. The outcomes are tabulated in the columns.

Half get one treatment, half the other (or none). In an experiment, you manipulate variables.This design is also called a case-control study. Enter the number with low exposure in one row, and the number with high exposure in the other row. Then you would assess EMF exposure in all subjects. To perform a retrospective study of the EMF-leukemia link, you would recruit one group of subjects with leukemia and a control group that does not have leukemia but is otherwise similar. A retrospective case-control study starts with the condition being studied and looks backwards at potential causes.Subjects that get leukemia are tabulated in one column the rest are tabulated in the other column. Then you would follow all subjects over time and tabulate the numbers that get leukemia. These two groups define the two rows in the table.

To perform a prospective study of the EMF-leukemia link, you would select one group of subjects with low exposure to EMF and another group with high exposure.

A prospective study starts with the potential risk factor and looks forward to see what happens to each group of subjects.

It would not be a cross-sectional study if you selected subjects based on EMF exposure or on the presence of leukemia. You then check the subjects to see whether or not they have leukemia. You would assess whether or not each subject has been exposed to high levels of EMF. To perform a cross-sectional study of the EMF-leukemia link, you would need to study a large sample of people selected from the general population. As an example, let's consider how to conduct a cross-sectional study of the link between electromagnetic fields (EMF) and leukemia.

In a cross-sectional study, you recruit a single group of subjects and then classify them by two criteria (row and column).

artery obstructed).Ĭontingency tables display data from these five kinds of studies: Contingency tables summarize results where you compared two or more groups and the outcome is a categorical variable (such as disease vs.