In this self-selected sample
of active duty Soldiers aged 40 and older, about one-half of those who were offered cardiovascular risk assessment at the jobsite agreed to participate.
This involved slight deception at the onset in order to avoid any stigmatization of NSSI or a self-selected sample
as noted by Gratz (2006).
The nonfunded schools also represented a self-selected sample
, and the 14 nonfunded schools with survey data from both 1999 and 2000 represented only 6% of all nonfunded Oregon schools.
* Using a self-selected sample. This is a major problem with call-in polls or surveys that are posted on a Web site -- only those who really want to say something about the topic will participate.
Self-selected samples generally provide very polarized responses -- people who love you or hate you will reply, but those who just don't care won't bother.
This non-randomized, self-selected sample
represents a "treatment as usual" group.
Note that a huge self-selected sample
is usually less accurate than a much smaller probability sample.
Therefore, each equation would be estimated based on a self-selected sample
. In the college graduate group, for example, the wage equation estimated using the self-selected sample
As a result, it is not ensured that the estimated birthweight production function using the self-selected sample
is an unbiased representative of the total population.(2)
COLF'S assistant director Leah Singh in a letter to the National Post criticized the Hastings report for its flawed methodology, mainly the "inadequately sized, self-selected samples
" used to draw its conclusions.
Weaknesses in previous studies (including self-selected samples
, inadequate statistical power and reliance on self-reported outcomes) make it impossible to conclude that a two-method strategy for dual protection is more appropriate to promote than a one-method approach.
We recruited the self-selected samples
of workers through in-plant publicity and with assistance from managers.