A regular traveler is planning an overseas trip but hasn’t purchased her plane ticket. So she visits various websites that can predict whether the cost of her ticket will rise or fall.
Two sites say the likelihood of an imminent price increase are, respectively, 60 percent and 50 percent. Our traveler does the math and averages the odds at 55 percent.
She then tries two other websites, and both give their predictions in verbal form: An increase, the sites agree, is “likely.” From this, the traveler concludes that the chance of a price hike is “very likely.”
This curious difference in how numeric and verbal predictions are calculated is noted in new research, forthcoming in the journal Management Science, by Johns Hopkins University marketing professor Robert Mislavsky. In a series of eight experiments with over 7,000 participants, Mislavsky and co-author Celia Gaertig of the University of Chicago found that people viewing more than one numeric probability forecast averaged the figures, leading to a lower number than the highest given – as in the 55-percent example above.
However, when the participants looked at multiple forecasts in verbal form, they reached a more certain conclusion than that seen in any of the individual forecasts – as in the other example above, with two predictions of “likely” leading to a determination of “very likely.”