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One of the most common questions I hear is how to enter and analyze data from a two by two crosstabulation. It is not immediately obvious, especially to beginners, how to get started with this type of data. This is part 1 of a series of 6 handouts on this topic (view handouts 2, 3, 4, 5, 6). There is also a video version of this topic. Part 1explains how to take information from a published study and display it as a two by two table.
A two by two tabular display includes nine numbers, 4 cell counts, 2 row totals, 2 column totals, and 1 grand total. Most papers will display only some of the nine numbers, but you can usually construct the missing numbers with a bit of care and patients. Here is how you would do it for a particular example.
First, label the rows and columns. Traditionally, the rows represent the risk factor and the columns represent the outcome.
Then fill in the numbers that you are given.
Then use a bit of arithmetic to fill in the remaining gaps.
This is what the final two by two table looks like:
