How does an outlier affect the mean and media for a data set?

An outlier can significantly affect the mean of a data set by pulling it in the direction of the outlier, leading to a potentially misleading representation of the central tendency. In contrast, the median, which is the middle value of a sorted data set, is less affected by outliers, providing a more robust measure of central tendency. Therefore, while the mean may change dramatically with the presence of an outlier, the median remains relatively stable, making it a preferred measure in skewed distributions.