While the methodology included use of data from Medicare claims to adjust for confounding factors, including self-selection bias
, our estimated savings might still have been overstated due to persistent selection effects.
But, because there is a likely self-selection bias
in the sample, unobserved variables in the regression may be correlated with announcement returns.
This finding may be a result of self-selection bias
; that is, mothers who feel depressed during pregnancy may choose not to return to work, or to delay their return to work, following their delivery.
The high response rate (66%) is in line with other quality surveys of physicians. Having such a good response rate minimizes the possibility of a self-selection bias
and assures external validity.
Once again, the title of the experiment created a self-selection bias
such that the volunteers for the erotica study reported more sexual experience, and females in the erotica study were less erotophobic than the female volunteers in the nonsexual experiment.
A wide range of behaviors were included, and self-selection bias
remained a problem because the survey was voluntary.
While the survey's methodology report does not include a specific margin of error, it notes that the risk of self-selection bias
was greatly reduced because participants did not know the subject matter of the study until after they signed up to complete it.
He is also keenly aware of the problems of self-selection bias
in sampling students who seek tutoring and how this bias can invalidate the numbers we might present showing efficacy.
These analyses controlled for men's social and demographic characteristics (age, marital status and education) at the end of the initial uial interval, allowing the researchers to assess whether self-selection bias
Consequently, self-selection bias
should be minimized.
Rogers cautions that the study's results are mitigated by a possible self-selection bias
: "People who enjoy walking may choose to live in more walkable neighborhoods," she said, adding that it would be naive to say this study "proves" that walkability affects social capital in neighborhoods.
Unfortunately, this study suffered from a serious self-selection bias
and a low response rate.