What is cochran-armitage test for trend?

The Cochran-Armitage test for trend is a statistical test used to identify trends in categorical data, typically used in epidemiological or biological research. The test assumes that the levels of a categorical variable are ordered, for example, low, medium, and high, and that there is a linear relationship between the level and a binary outcome variable. The test is used to determine whether the proportion of an outcome variable increases or decreases across ordered categories. The test statistic is an approximation of the slope of the trend line between the categorical variable and the outcome variable. The Cochran-Armitage test is widely used in clinical trials, genetic association studies, and public health research. The test is named after William G. Cochran and Egon Armitage, who developed the method independently in the early 1950s.