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Notes on Topic 5:
Transforming Variables

    SAT Math and Verbal
    Population Parameters

    About the SAT Math Population Values
    Thanks to David Thissen and Lyle Jones, of UNC's Quantitative Psychology program for the following information.

    • When the SAT scales were originally standarized in the late 1940's they were given a mean of 500 and a standard deviation of 100. Since then there has been "slippage" in the means such that in recent years the mean Verbal score was about 430 and the mean Math score about 460 (with the standard deviations remaining about the same).

    • Clearly, the differential slippage of SAT means (from the standardization of the late 1940s) has been a source of confusion. Users would have been better advised to focus on percentile scores rather than scale scores on the "old" SAT reports. (The same is true for GRE scores!)

    • As of April 1, 1995, the SAT scales were changed so that the mean became (again) approximately 500 both Verbal and Math, with standard deviations of about 100. While that's "current", it is probably not the scale that most of you taking psych 30 would have scores on. Those would be on the old scale, where the mean Verbal was about 430 and Math about 460.

    • Last year's observed averages are reported in a story (they are 505 V, 508 Q). There is a complete table where old scores have been converted to the new recentered scale for comparison.

    • Finally, the College Board reports the standard deviation and percentiles from last year (they are reported as being 110 for Verbal, 112 for Quantitative), as well as the SAT's predictive validity (how well it predicts college performance) and reliability (how stable the scores are).