Sentences with phrase «possibility of selection bias»

Second, the attrition rates in this study were substantial, which of course introduces the possibility of a selection bias.

The quasi-experimental design reduces spillover effects and makes it easier to implement the program, but does not eliminate the possibility of selection bias.35, 36 The use of prospectively defined controls at quasi-experimental sites likely contributed to minimized discrepancies in outcomes between randomization and quasi-experimental groups.37 For several parenting outcomes, such as discipline practices, findings were of similar magnitude and direction at randomization and quasi-experimental sites, but statistically significant at only quasi-experimental sites, where the sample size was larger; they were significant in the pooled sample, as well.

The quasi-experimental design reduces spillover effects but does not eliminate the possibility of selection bias.41, 42 The use of prospectively identified control subjects was intended to minimize discrepancies in outcomes between the 2 designs.43 For some outcomes, as noted previously, the magnitude and direction of outcomes for intervention and control families at randomization and quasi-experimental sites were comparable, although they were statistically significant only at quasi-experimental sites and in the larger pooled sample.

The authors also acknowledge the limitations of their conclusions given problems arising from differences in market risk and the possibility of selection bias, a common problem also found when examining the performance of hedge funds.

In one study, a protective effect of breast milk on blood pressure was observed when 26 percent of the original cohort were followed up at ages 13 — 16 years (15), but not when 81 percent were examined at ages 7.5 — 8 years (16), suggesting either the possibility of selection bias in the later follow - up or an amplification of the breastfeeding — blood pressure association (49).

Another limitation of our study is the possibility of selection bias.

Not exact matches

From their description I don't think there is a bias in their sample of scientists, though there is always the possibility of self - selection, where people might be more likely to respond to a survey if it originates from a source who they perceive to be credible.

[Response: this is an interesting survey, and I think I took part... there are three concerns though: (1) self selection bias and (2) possibility of multiple returns from the particularly... avid (3) possibility of returns from non -(climate --RRB- scientists.

Such a measure excludes the possibility of editor bias in the selection of publications (as it asks scientists directly) as suggested in previous comments on Oreskes» article.