What does the statistics term "outlier" mean?
Outliers: The Story of Success by Malcolm Gladwell takes its name from the statistical concept of an "outlier", a data point very far away from other points in a data set. It can be determined using interquartile range or standard deviations. Often outliers are omitted from data sets before statistical analysis because they may constitute evidence of observational or statistical errors. For example, if you were studying human height, basketball players might be an extreme of the human norm, but if, in a list of heights, you saw a 66-foot tall human, you would need to discard this example as a data entry error. Thus the first step in your analysis would be looking at the actual statistical meaning of the term. Next would be thinking about whether Gladwell is really doing serious statistical analysis, or simply using "outliers" as a buzzword to cover what is actually anecdotal evidence.