What does it mean if data is described as skewed to the left?

When data is described as skewed to the left, it indicates that the distribution has a longer or fatter tail on the left side, while the bulk of the data values are concentrated on the right side. This shape implies that there are relatively few low values, which can pull the mean down, as the mean is sensitive to extreme values. In contrast, the median, which is less affected by outliers, will typically be higher than the mean in a left-skewed distribution.

This concept is crucial in statistics because the skewness of data can affect the choice of statistical analysis methods and interpretations of measures of central tendency. Understanding this characteristic helps in visualizing data behavior, making decisions about data transformation, and recognizing the need for specific statistical tests that assume normality or symmetry.