Abstract
In order to compare the relative precision of four formulas for calculating the standard deviation through using one of the IBM 360/ 370 family of computers and a program written in FORTRAN, various sets of test scores were employed. Each set consisted of approximately 5000 scores. Two of the formulas were in raw score form; one formula was the definitional deviation score formula; and the fourth was a modification of the latter. All four formulas are algebraically equivalent. The modified deviation score formula in every instance yielded the most nearly exact results. The raw score formula for the standard deviation that is most often used in computer programs often yielded the results with greatest error. Implications for the computation of other statistics are discussed, and recommendations are offered.
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