What characterizes an outlier in a data set?

An outlier is characterized as a value that is significantly higher or lower than the other values in a data set. This definition arises from the fact that outliers often deviate markedly from the central tendency of the data, which can be measured through the mean or median.

The presence of an outlier can heavily influence statistical analyses, leading to skewed results. For instance, in calculating the mean, an outlier can raise or lower the average significantly compared to the majority of the data points. Identifying outliers is essential for understanding the variability of data and ensuring the robustness of statistical conclusions drawn from the data set.

While it's crucial to acknowledge that other options present different concepts—such as the most frequently occurring value or the average—they do not adequately describe an outlier's defining characteristic of being an extreme value relative to the rest of the data.