¹Earlier rounds of NSOPF selected institutions that the U.S. Department of Education (ED) recognized as accredited. However, ED no longer distinguishes among institutions based on accreditation level. As a result, NCES now subdivides the postsecondary institution universe into schools that have Title IV participation agreements for federal financial assistance and those that do not.(return to text)

²Private for-profit institutions are not included even though they may be Title IV degree-granting institutions.(return to text)

³See A Classification of Institutions of Higher Education, The Carnegie Foundation for the Advancement of Teaching (Princeton, New Jersey, 1994).(return to text)

⁴The NSOPF:99 samples are not simple random samples and, therefore, simple random sample techniques for estimating sampling error cannot be applied to these data. The DAS takes into account the complexity of the sampling procedures and calculates standard errors appropriate for such samples. The method for computing sampling errors used by the DAS involves approximating the estimator by the linear terms of a Taylor series expansion. The procedure is typically referred to as the Taylor series method.(return to text)

⁵A Type I error occurs when one concludes that a difference observed in a sample reflects a true difference in the population from which the sample was drawn, when no such difference is present.(return to text)

⁶U.S. Department of Education, National Center for Education Statistics, A Note from the Chief Statistician, no. 2, 1993.(return to text)

⁷The standard that p<.05/k for each comparison is more stringent than the criterion that the significance level of the comparisons should sum to p<.05. For tables showing the t statistic required to ensure that p<.05/k for a particular family size and degrees of freedom, see Olive Jean Dunn, “Multiple Comparisons Among Means,” Journal of the American Statistical Association 56 (1961): 52–64.(return to text)

⁸More information about ANOVA and significance testing using the F statistic can be found in any standard textbook on statistical methods in the social and behavioral sciences.(return to text)

⁹For more information about least squares regression, see Michael S. Lewis-Beck, Applied Regression: An Introduction, Vol. 22 (Beverly Hills, CA: Sage Publications, Inc., 1980); William D. Berry and Stanley Feldman, Multiple Regression in Practice, Vol. 50 (Beverly Hills, CA: Sage Publications, Inc., 1987).(return to text)

¹⁰See John H. Aldrich and Forrest D. Nelson, “Linear Probability, Logit and Probit Models” (Quantitative Applications in Social Sciences, Vol. 45) (Beverly Hills, CA: Sage, 1984). Analysts who wish to estimate other types of models can apply for a restricted data license from NCES.(return to text)

¹¹The adjustment procedure and its limitations are described in C.J. Skinner, D. Holt, and T.M.F. Smith, eds., Analysis of Complex Surveys (New York: John Wiley & Sons, 1989).(return to text)