Binary classification

Binary or binomial classification is the task of classifying the elements of a given set into two groups on the basis of a classification rule. Some typical binary classification tasks are:

An important point is that in many practical binary classification problems, the two groups are not symmetric – rather than overall accuracy, the relative proportion of different types of errors is of interest. For example, in medical testing, a false positive (detecting a disease when it is not present) is considered differently from a false negative (not detecting a disease when it is present).