¹ The U.S. Department of Education is no longer distinguishing among institutions based on accreditation level. As a result, NCES now subdivides the postsecondary institution universe into schools that receive Title IV federal financial assistance and those that do not.(return to text)

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

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

⁴ However, the institution survey of NSOPF:99 added one question pertinent to teaching assistants, which asked institution respondents to estimate the percentage of undergraduate student credit hours assigned to teaching assistants. This question allows exploration of the issue of using teaching assistants in undergraduate education.(return to text)

⁵ Instructional duties include teaching credit courses or supervising students' academic activities for credit.(return to text)

⁶ However, estimates presented in table 2 were computed with the SUDAAN program software because there is no DAS for the institution survey. The standard errors for estimates produced by SUDAAN were based on the Taylor-series approximation method. For more information about the SUDAAN program software, see the SUDAAN Users Manual (Shah, Barnwell, and Bieler 1995).(return to text)

⁷ The 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)

⁸ A Type I error occurs when one erroneously concludes that a difference observed in a sample reflects a true difference in the population from which the sample was drawn.(return to text)

⁹ U.S. Department of Education, National Center for Education Statistics, A Note from the Chief Statistician, no. 2, 1993.(return to text)

¹⁰ Ibid.(return to text)

¹¹ The 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)

¹² More 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)

¹³ For 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)

¹⁴ Although the DAS simplifies the process of making regression models, it also limits the range of models. Analysts who wish to use other than pairwise treatment of missing values or to estimate probit/logit models (which are the most appropriate for models with categorical dependent variables) can apply for a restricted data license from NCES. See John H. Aldrich and Forrest D. Nelson, Linear Probability, Logit and Probit Models (Quantitative Applications in Social Sciences, Vol. 45) (Beverly Hills, CA: Sage University Press, 1984).(return to text)

¹⁵ The 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)