Why the Average Can Mislead: Outliers, Skew and Weights
An average is a summary, and summaries hide things. Here are the three situations where the usual mean gives a misleading answer, with numbers you can check.
Articles, page 11
Plain-English guides to the numbers in everyday life: how a calculation works, where people go wrong, and which tool to reach for.
Z-Scores Explained: Comparing Values on Different Scales
A z-score re-expresses any value as a number of standard deviations from the mean, which lets you compare results that use different scales.