What does the term "outlier" refer to in a statistical data set?

The term "outlier" refers to a data point that is significantly different from the other values in a data set. This means that an outlier is either much higher or much lower than the majority of the data points, which can skew the results of statistical analyses and impact measures such as the mean and standard deviation.

Identifying outliers is crucial in statistics as they can provide insights into variability in the data, reveal errors in data collection, or signify important variations or discrepancies that warrant further investigation. While options discussing extreme values may seem relevant, they don't capture the importance of the differing nature of an outlier in comparison to the dataset as a whole. Options that mention frequency or being within an average range do not align with the definition of an outlier either, as they describe regular data points rather than the exceptional cases that outliers represent.