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.'