Stimulus Sampling and Social Psychological Experimentation

The authors discuss the problem with failing to sample stimuli in social psychological experimentation. Although commonly construed as an issue for external validity, the authors emphasize how failure to sample stimuli also can threaten construct validity. They note some circumstances where the need for stimulus sampling is less obvious and more obvious, and they discuss some well-known cognitive biases that can contribute to the failure of researchers to see the need for stimulus sampling. Data are presented from undergraduate students (N = 106), graduate students (N = 72), and psychology faculty (N = 48) showing insensitivity to the need for stimulus sampling except when the problem is made rather obvious. Finally, some of the statistical implications of stimulus sampling with particular concern for power, effect size estimates, and data analysis strategies are noted.