After controlling for potential nonrandom selection
, the coefficient on the HSCT variable measures the treatment effect, that is, the difference in the probability of death that exists between HSCT recipients and those who underwent alternative treatments.
into experiments poses significant challenges in extrapolating findings to the real world (i.
In our study, however, we are not able to control for nonrandom selection
into caregiving among parents or spouses.
Unfortunately, the potential bias created by nonrandom selection
into employment is even more severe for fathers than mothers -- most nonworking men are involuntarily unemployed and probably do not devote much of the extra nonmarket time to investments in children.
GAO's analysis, including a review of a nonrandom selection
of contracts, indicates that the U.
Here is the answer: Subsequent to these random events, the system (antibody-secreting cell, or entire organism) is put through a very nonrandom selection
For example, if parents who really value education were more likely to pull their children out of a cohort with a particularly high proportion of peers from troubled families, such nonrandom selection
would cause us to erroneously attribute lower performance to the presence of the troubled peers.
A matrix of t-tests was constructed if nonrandom selection
of habitats occurred (P < 0.
This variation is then subjected to nonrandom selection
Given the possibility of nonrandom selection
into treatment, there are two broad approaches to estimating the effects of treatment.
Our survey, although limited by the small sample size (24 buildings) and the nonrandom selection
of sites, strongly suggests that caulking installed before the ban in 1977 may pose a significant public health hazard.
Even though the composition of the sample turned out to be similar to that of the entire school, the nonrandom selection
process may still have biased the results.