The National Postsecondary Student Aid Study (NPSAS) is a comprehensive nationwide study conducted by the U.S. Department of Education’s National Center for Education Statistics (NCES) to determine how students and their families pay for postsecondary education.1 It also describes demographic and other characteristics of students enrolled in the 50 states, the District of Columbia, and Puerto Rico. The NPSAS study is based on a nationally representative sample of all students in postsecondary education institutions, including undergraduate, graduate, and first-professional students. Information is collected from institutions, student interviews, and government data files. For this study, data were analyzed for undergraduates from four administrations of the NPSAS survey: NPSAS:1990, NPSAS:1993, NPSAS:1996 and NPSAS:2000. These surveys each represent more than 16 million undergraduates who were enrolled at some point between July 1 and June 30 of the survey years. The institutional weighted response rates for these NPSAS administrations all exceeded 85 percent as discussed in the next sections.
Overall Weighted Response Rates
The NPSAS:1990 survey achieved an overall weighted response rate of 86 percent among institutions. For the student Computer Assisted Telephone Interviews (CATI), the response rate was 76 percent.2 The overall weighted response rates for the NPSAS:1993 study were 88 percent among institutions and 67 percent among students.3 NPSAS:1996 had an institutional response rate of 91 percent and a student CATI response rate of 76 percent.4
For NPSAS:2000, the institutional response rate was 95 percent and the weighted overall student interview response rate was 66 percent.5 Because the student telephone interview response rate for NPSAS:2000 was less than 70 percent in some institutional sectors, an analysis was conducted to determine if estimates were significantly biased due to CATI nonresponse. Considerable information was known for CATI nonrespondents and these data were used to analyze and reduce the bias. The distributions of several variables using the design-based, adjusted weights for study respondents (study weights) were found to be biased before CATI nonresponse adjustments. The CATI nonresponse and poststratification procedures, however, reduced the bias for these variables; and the remaining relative bias ranged from 0 to 0.35 percent.6
The overall institutional response rate could be interpreted as the estimated percentage of eligible institutions that would provide a student enrollment list or database that could be used for sample selection. The overall CATI response rate is computed as the product of the weighted CATI response rate and the institutional response rate.
The weight variable used for analysis of this report is PSKEEPWT, NP93WT, DASWT1 and STUDYWT for NPSAS:1990, NPSAS:1993, NPSAS:1996 and NPSAS:2000, respectively, which includes all undergraduates in the NPSAS surveys, including those without a telephone interview.
Item Response Bias
All the variables used in this report and defined in appendix C had item response rates above 85 percent. Therefore, a bias analysis for individual survey items was not necessary.