When estimating risks, people may use "50" as an expression of the verbal p
hrase "fifty-fifty chance," without intending the associated number of 50%.
The result is an excess of 50s in the response distribution. The present s
tudy examined factors determining the magnitude of such a "50 blip," using
a large sample of adolescents and adults. We found that phrasing probabilit
y questions in a distributional format (asking about risks as a percentage
in a population) rather than in a singular format (asking about risks to an
individual) reduced the use of "50." Less numerate respondents, children,
and less educated adults were more likely to say "50," Finally, events that
evoked feelings of less perceived control led to more 50s. The results are
discussed in terms of what they reveal about how people express epistemic
uncertainty. (C) 2000 Academic Press.