Nonresponse Effects on Relationships Between Variables

To examine nonresponse effects on variable relationships, data from a panel study of 1,870 older Iowa residents are reported. When data are accumulated by wave of response, differences are minor on variable distributions (percentage, mean, standard deviation), bivariate relationships (correlation), and multivariate relationships (regression), suggesting that the assumed impact of nonresponse bias on variable relationships has been overstated. Willis J. Goudy is an Associate Professor in the Department of Sociology and Anthropology, Iowa State University, Ames, Iowa. Journal Paper No. J-8362 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2010. This investigation was supported in part through grant number 10-P-57495/7-01 from the Social Security Administration, Washington, D. C. The author wishes to thank Richard D. Warren and Charles L. Mulford for their helpful comments on an earlier draft of this article. POQ 40 (1976) 360-369 This content downloaded from 157.55.39.253 on Sat, 11 Jun 2016 06:23:35 UTC All use subject to http://about.jstor.org/terms NONRESPONSE EFFECTS 361 not to influence relationships between variables, and Schwirian and Blaine (1966-67) observed similar results in two of three tests. The third case of Schwirian and Blaine, plus the work of Lehman (1963) and especially Mulford et al. (1974), found nonresponse bias affecting conclusions generated from analyzed relationships. The present study examines the impact of nonresponse bias on individual items and on bivariate and multivariate relationships. The Work and Retirement Study To examine nonresponse bias to a mail questionnaire, data from a panel study of older Iowa residents are reported. The "work and retirement" research was initiated when interviews were conducted with a sample of fully employed males fifty years of age and older (Bauder and Doerflinger, undated). The 1,870 Iowans were living in or near 42 communities with from 2,500 to 10,000 population and were sampled from five occupational categories: self-employed professionals, salaried professionals, business proprietors, factory workers, and farmers. The occupational classes studied, of course, did not represent all occupational groups in nonmetropolitan midwestern communities, nor were they necessarily the most important. They did, however, include the self-employed and the salaried or wage worker, the professional and the nonprofessional, and the agricultural and nonagricultural worker. For each occupational category, sampling rates within the communities were determined so that a uniform statewide rate was maintained. The interview instrument contained questions on work history and satisfaction, retirement plans and attitudes, mobility, family and kin networks, social participation, health, and general sociodemographic information. Two years after they completed the interview, respondents were sent a brief mail questionnaire, which stressed changes in the employment situation plus evaluations of health and social participation changes. Three waves were mailed; those not responding to the first questionnaire were sent a replacement, and those not completing the second copy were sent a third. Of the initial 1,870 interview respondents, 87 percent completed the mail questionnaire, 3 percent were deceased, 5 percent were never recontacted, less than 1 percent were too ill or senile, 3 percent refused, and records were insufficient to classify the remaining 1 percent.2 Thus, over 90 percent of those thought to be living at the time of the second phase cooperated by completing the questionnaire. In the analysis that follows, sociodemographic information (age, marital status, education, income) from the interviews was used as the base. Additional interview variables included a one-item measure of morale 2 The 31 unclassified cases represent a hazard of longitudinal research, especially when the data are the subject of secondary analysis as in this study. This content downloaded from 157.55.39.253 on Sat, 11 Jun 2016 06:23:35 UTC All use subject to http://about.jstor.org/terms