The people who responded to the survey differ from the general population in many respects; most significantly, they are actual or would-be cheaters.
Previous research has shown that generally people who self-select into a (web) survey differ from those who do not with respect to socio-demographics but also in terms of time availability, web skills, or altruism to contribute to the project (Bethlehem 2010; Couper et al. 2007; Malhotra & Krosnick 2007).
Before we proceed to that argument, notice that we are starting to see how the philosophical motivations of the work we are surveying differ from program to program; the contrast between psychologistic and anti-psychologistic agendas is not the only, or even the most important, dimension of variation.
It is not known if those who responded to the survey differ from those who did not.
This phenomenon where data collected in the first cycle of a survey differ from those collected in the following cycles is not uncommon [ 59].
A second concern is whether the practitioners responding to this survey differ from TMB practitioners in general, i.e., if non-respondents train in more, fewer, or different therapies, or have very different work habits or environments.
Although analyses of these data show that those who are harder to reach do not differ a great deal from those who are easier to reach (Wennberg et al., forthcoming), we cannot know whether those not responding to the survey differ from our sample.
Researchers have observed that important concerns include coverage bias (bias due to sampled individuals not having or choosing not to access the Internet) and nonresponse bias (bias due to participants of a survey differing from those who did not respond in terms of demographic or attitudinal variables) (Kim et al. 2011).
Nycteris also shows the highest rate of non-synonymous change at exon 17 of all species surveyed, differing from both the mammalian consensus and its closest relative by eight amino acids (V678A, A680T, T692A, E698A, L699F, D701E, I705E, L710S; table S4).
We identified those patients whose self-reported date of stroke onset from the survey differed from the date of presentation to the ED captured by the medical chart.
