Slide 17 of 38
Notes:
I moved this slide from where it is in your handouts. (Check the 2nd or 3rd page from the end)
Subject Characteristics - Selected on a non-random basis; members of a certain group perhaps
Mortality - Loss of subjects: transfers, promotions, retirement, death
Location - Different environments have different resources or different distractions
Instrumentation -Problem with the testing instrument or observer
Maturation - Any change that occurs because of time passing
Regression -Move to the mean if participants were chosen specifically because of very high scores or very low scores
Hawthorne Effect - change simply because subjects were assigned to a treatment group. Can be a negative change (see text p. 197)
History - Unanticipated/unforeseen event. Sprinklers go off in the middle of the study. Blizzard closes down the company in the middle of the project.
Implementation -Flaw in the way a study was conducted