The fact that the Learning Module respondents differed somewhat from the nonrespondent
workers suggests some degree of self-selection, about which we say more below.
After the completion data collection, all nonrespondents
were asked to participate in a shorter version of the survey that contained five items intended to assess the relationship between fan identification and survey participation.
Telephone follow-up calls are made to nonrespondents
prior to the publication deadline.
This list, combined with our survey responses and information from the thesis supervisors of nonrespondents
, led us to estimate the size of the 1996-1997 class at roughly 950 graduates.
Note that if there is a 100-percent response rate (RR = 1), or if there is no difference between the respondent and nonrespondent
1996) first suggested using data averages across resident ZIP codes and Census tracts to model the differences between survey respondents and nonrespondents
and control for nonresponse bias through a sample selection model.
What is also problematic with the methodology is that, statistically speaking, even if the nonrespondent
calls had been randomly selected, which the authors do not tell us, the results are still spurious.
were mailed a second copy of the survey packet after three weeks had elapsed.
The comparative statistics presented in Table 1, Panel B reveal no significant differences between respondent and nonrespondent
firms, thus suggesting that nonresponse bias is not a concern.
Initially, random sample mailings were administered to 6,000 businesses across the state followed by telephone interviews of nonrespondents
analyses revealed no statistically significant differences in all cases.
Responses from the second mailing were statistically compared to the first twenty responses of the first mailing and were negative for nonrespondent