Standard Errors

When data from sample surveys are reported, as is the case with most of the indicators in The Condition of Education, the standard error is calculated for each estimate. The standard errors for all estimated totals, means, medians, or percentages reported in the supplemental tables of The Condition of Education can be viewed at the NCES website (http://nces. ed.gov/programs/coe).

The standard errors of the estimates for different subpopulations in an indicator can vary. As an illustration, indicator 14 reports the average mathematics scores of 13-year-old students between 1973 and 2008. In both 1994 and 1996, the average mathematics score for 13-year-olds was 274 (see table A-14-2). In contrast to the similarity of these scores, the standard errors for these estimates were 0.9 and 1.0, respectively (see table S-14-2). The average score with the smaller standard error provides a more reliable approximation of the true value than does the average score with a higher standard error. In addition, standard errors tend to diminish in size as the size of the sample (or subsample) increases.

For indicator 17, which reports median annual earnings, special procedures are followed for computing the standard errors for these medians. See appendix G of the source and accuracy statement for the Current Population Study (CPS) 2008 Annual Social and Economic supplement (ASEC) for information on how to calculate the standard errors (http://www.census.gov/apsd/techdoc/cps/cpsmar08.pdf).