forecastingprinciples.com Reviews of Important Papers on Forecasting
Before 1985 Reviews
Review of:

Ruth Hamill, T. D. Wilson and R. E. Nisbett (1980), “Insensitivity to sample bias; generalizing from atypical cases," Journal of Personality and Social Psychology, 39, 578-589.


Vivid examples have a strong impact on people's attitudes–much stronger it seems, than carefully prepared statistical summaries from large sample. This generalization is drawn from prior research as well as from the two clever experiments reported in this paper. The experiments have implications for the presentation of forecasts, as well as for the use of information to support a forecast. Of particular interest for the presentation of a forecasts is the use of scenarios. A vivid scenario would be expected to appear to be likely. According to this study, an event described in a scenario will be regarded as more likely even if the scenario was identified as being atypical or unlikely. This might be useful if one is trying to gain some attention for contingency planning. But scenarios may be dangerous if used to make predictions. Alternatively, vivid scenarios may help to improve estimates in cases where people seriously underestimate the probability. (Perhaps this is the intention of Ground Zero Demonstrations?) In the presentation of data, the choice of examples seems to influence people's attitudes more than the statistical information, even when the example is identified as being atypical. To avoid bias in presentation, one should select typical examples. The dangers of atypical examples should be recognized; even more powerful than 'lying with statistics' is the opportunity of 'lying with examples.'