¹For more information on the NPSAS survey, consult the methodology report (Riccobono et al. 2002). Additional information is also available at the NPSAS website http://nces.ed.gov/npsas. (return to text)

²The overall CATI/CAPI weighted response rate was computed as the product of the weighted student CATI/CAPI yield and the weighted institutional yield.. (return to text)

³Public 2-year and private not-for-profit 2-year or less institutions each had a weighted student CATI/CAPI response rate of 69 percent. Private for-profit less-than-2-year institutions had a weighted student CATI/CAPI response rate of 67 percent. (return to text)

⁴ For nonresponse bias analysis, see Siegel et al. (2002), available at http://nces.ed.gov/pubsearch/pubsinfo.asp?pubid=200203. (return to text)

⁵The NPSAS 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)

⁶A 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)

⁷U.S. Department of Education, National Center for Education Statistics, A Note from the Chief Statistician, no. 2, 1993. (return to text)

⁸Ibid. (return to text)

⁹The 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 Dunn (1961). (return to text)