(they were then based in brooklyn). recent immigrants to the us from eastern europe unfamiliar with the sport of baseball got the answer wrong, and this was used to infer that eastern europeans had lower intelligence. the question did not measure intelligence: it only measured how long one had lived in the us and become accultured to a popular pastime. researcher expectations may be communicated unintentionally to the participants non-verbally, eliciting the desired effect. to control for this possibility, double-blind experimental designs should be used where possible. that is, the evaluator of a particular participant should be unaware of what intervention has been performed on that particular participant or should be independent of the experimenter. defining predicted outcome too narrowly. for instance, using only job satisfaction to measure happiness will exclude relevant information from outside the workplace. confounding variables (covariates): the root cause for the observed effects may be due to variables that have not been considered or measured. an in-depth exploration of the threats to construct validity is presented in trochim.