Outlier Analysis

An outlier is a data point that differs significantly from other data points within a give data set. Sometimes referred to as abnormalities, anomalies, or deviants, outliers can occur by chance in any given distribution. In large samples, there is an expectation of a small number of outliers and their presence alone does not suggest any anomaly and should not generate concern over the entire data set. However, outliers can also be indicative of measurement error, a skewed distribution, or data points from a different underlying distribution. Many statistical tests are sensitive to the presence of outliers and therefore the ability to detect an outlier is an important part of data analysis. Typically outliers are recording and measurement errors or incorrect distribution assumptions but can ...