Editing Contingency table (section)

==Example==
Suppose there are two variables, sex (male or female) and [[handedness]] (right- or left-handed). Further suppose that 100 individuals are randomly sampled from a very large population as part of a study of sex differences in handedness. A contingency table can be created to display the numbers of individuals who are male right-handed and left-handed, female right-handed and left-handed. Such a contingency table is shown below.

{| class="wikitable" style="margin-left:auto;margin-right:auto;text-align:center;"
! {{Diagonal split header|Sex|Handed-<br />ness}} !! Right-handed !! Left-handed !! Total
|-
! Male
| 43 || 9  || 52
|-
! Female
| 44 || 4  || 48
|-
! Total
| 87 || 13 || 100
|}
The numbers of the males, females, and right- and left-handed individuals are called [[marginal total]]s. The grand total (the total number of individuals represented in the contingency table) is the number in the bottom right corner.

The table allows users to see at a glance that the proportion of men who are right-handed is about the same as the proportion of women who are right-handed although the proportions are not identical. The strength of the association can be measured by the [[odds ratio]], and the population odds ratio estimated by the [[sample odds ratio]]. The [[statistical significance|significance]] of the difference between the two proportions can be assessed with a variety of statistical tests including [[Pearson's chi-squared test]], the [[G-test|''G''-test]], [[Fisher's exact test]], [[Boschloo's test]], and [[Barnard's test]], provided the entries in the table represent individuals randomly sampled from the population about which conclusions are to be drawn. If the proportions of individuals in the different columns vary significantly between rows (or vice versa), it is said that there is a ''contingency'' between the two variables. In other words, the two variables are ''not'' independent. If there is no contingency, it is said that the two variables are ''independent''.

The example above is the simplest kind of contingency table, a table in which each variable has only two levels; this is called a 2&nbsp;×&nbsp;2 contingency table. In principle, any number of rows and columns may be used. There may also be more than two variables, but higher order contingency tables are difficult to represent visually. The relation between [[ordinal variable]]s, or between ordinal and categorical variables, may also be represented in contingency tables, although such a practice is rare. For more on the use of a contingency table for the relation between two ordinal variables, see [[Goodman and Kruskal's gamma]].