sten scores

A sten score indicates an individual's approximate position (as a range of values) with respect to the population of values and, therefore, to other people in that population. The individual sten scores are defined by reference to a standard normal distribution. Unlike stanine scores, which have a midpoint of five, sten scores have no midpoint (the midpoint is the value 5.5). Like stanines, individual sten scores are demarcated by half standard deviations. Thus, a sten score of 5 includes all standard scores from -.5 to zero and is centered at -0.25 and a sten score of 4 includes all standard scores from -1.0 to -0.5 and is centered at -0.75. A sten score of 1 includes all standard scores below -2.0. Sten scores of 6-10 "mirror" scores 5-1. The table below shows the standard scores that define stens and the percent of individuals drawn from a normal distribution that would receive sten score.

class="wikitable" style="text-align: center;" |+ Standard/z scores, percentages, percentiles, and sten scores ! z-scores |width="9%"| < −2.0 |width="9%"|−2.0 … −1.5 |width="9%"|−1.5 … −1.0 |width="9%"|−1.0 … −0.5 |width="9%"|−0.5 … −0.0 |width="9%"|+0.0 … +0.5 |width="9%"|+0.5 … +1.0 |width="9%"|+1.0 … +1.5 |width="9%"|+1.5 … +2.0 |width="9%"|> +2.0
Percent | 2.28% || 4.41% || 9.18% || 14.99% || 19.15% || 19.15% || 14.99% || 9.18% || 4.41% || 2.28%
Percentile | 1.14 || 4.48 || 11.27 || 23.36 || 40.43 || 59.57 || 76.64 || 88.73 || 95.52 || 98.86
Sten | 1 || 2 || 3 || 4 || 5 || 6 || 7 || 8 || 9 ||10

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Percentiles are the percentile of the sten score (which is the mid-point of a range of z-scores).

Sten scores (for the entire population of results) have a mean of 5.5 and a standard deviation of 2.McNab, D. et al Career Values Scale: Manual & Users' Guide, Psychometrics Publishing, 2005.

When the score distribution is approximately normally distributed, sten scores can be calculated by a linear transformation: (1) the scores are first standardized; (2) then multiplied by the desired standard deviation of 2; and finally, (3) the desired mean of 5.5 is added. The resulting decimal value may be used as-is or rounded to an integer.

For example, suppose that scale scores are found to have a mean of 23.5, a standard deviation of 4.2, and to be approximately normally distributed. Then sten scores for this scale can be calculated using the formula, $\backslash frac\; \{(s\; -\; 23.5)\}\{4.2\}\; 2\; +\; 5.5$. It is also usually necessary to truncate such scores, particularly if the scores are skewed.

An alternative method of calculation requires that the scale developer prepare a table to convert raw scores to sten scores by apportioning percentages according to the distribution shown in the table. For example, if the scale developer observes that raw scores 0-3 comprise 2% of the population, then these raw scores will be converted to a sten score of 1 and a raw score of 4 (and possibly 5, etc.) will be converted to a sten score of 2. This procedure is a non-linear transformation that will normalize the sten scores and usually the resulting stens will only approximate the percentages shown in the table. The 16PF Questionnaire uses this scoring method.Russell, M.T., & Karol, D. (2002). The 16PF Fifth Edition administrator's manual. Champaign, IL: Institute for Personality and Ability Testing

Category:Psychometrics