Kontingenssitaulua

Kontingenssitaulu, known in English as a contingency table or cross-tabulation, is a type of table in statistics that displays the frequency distribution of variables. It is used to study the relationship between two or more categorical variables. The table is structured so that the rows represent the categories of one variable and the columns represent the categories of another variable. The cells within the table show the number of observations that fall into each combination of categories.

The primary purpose of a contingency table is to help researchers understand if there is a dependence between the variables being studied. By examining the distribution of frequencies across the cells, one can observe patterns and make inferences about the association. For example, a 2x2 contingency table might be used to compare the effectiveness of a new drug versus a placebo by looking at the number of patients who recovered and those who did not, categorized by whether they received the drug or the placebo.

Statistical tests, such as the chi-squared test of independence, are often applied to contingency tables to formally assess whether the observed association between variables is statistically significant or likely due to random chance. The degrees of freedom for such tests are calculated based on the number of rows and columns in the table. Contingency tables are a fundamental tool in descriptive statistics and are widely used in various fields, including social sciences, medicine, and market research, for summarizing and analyzing categorical data.