A crowd's estimate beats its members because unbiased errors cancel, but the median is the statistic, not the mean. At Galton's 1906 fair the crowd's figure for the ox was 1,197 pounds against 1,198. In years of jelly-bean guesses in his classes Malone finds the mean often far off, with 20 to 40 percent of students beating it, while the median holds; Galton himself used the median.

Evidence 4 passages

• groundsSuperminds (audiobook machine transcript), Thomas W. Malone

  a number of other researchers have similarly found that the median is a better way of combining a group's guesses than the average.

• groundsSuperminds (audiobook machine transcript), Thomas W. Malone

  20 to 40 percent of the class members often make guesses that are more accurate than the average.

• groundsSuperminds (audiobook machine transcript), Thomas W. Malone

  When you average their answers, the errors should cancel each other out, leaving an accurate estimate.

• groundsSuperminds (audiobook machine transcript), Thomas W. Malone

  It turned out that the average of all the guesses, 1,197 pounds, was a remarkably accurate estimate of the actual weight, 1,198 pounds.

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