Fat Chance: Writing about Probability
Posted by Armando Brito Mendes | Filed under Data Science, estatística
Bons conselhos sobre como comunicar incerteza, probabilidades e percentagens
Since the COVID-19 pandemic began, almost every choice we have made in our day-to-day lives has required careful consideration of the odds. How dangerous is going to the supermarket at peak time? Is it safe to see friends after getting one vaccine shot? Will children get sick, or spread the virus to others, if they go back to school?
Just the quantity of decisions can be exhausting. But there’s something else making all of these choices so difficult: People, by and large, are bad at probability. We turn high odds into certainties, as when people assume that the accuracy of PCR tests for COVID means they’ll always yield correct results, or when we think of relatively unlikely events, like catching the virus after being fully vaccinated, as impossible. And in between 100 percent certainty and zero chance, the way we interpret any given number can change radically based on how that probability is expressed.
Such glitches in thinking aren’t surprising, says journalist and statistician Regina Nuzzo, a professor of statistics at Gallaudet University in Washington, DC, and a senior advisor for statistics communication and media innovation at the American Statistical Association. “Human brains hate probability, they hate ambiguity, they hate the uncertainty,” she says. “We’re just not wired to deal with this sort of thing very well.”
But for science writers, avoiding uncertainty isn’t an option. “Everything [in science] is quantified by the likelihood or lack of likelihood of it happening,” says science journalist Tara Haelle, who has written extensively about covering statistics for the Association of Health Care Journalists (AHCJ). But as Haelle says, “Humans don’t make decisions that way.” People tend to be far more comfortable with a definitive yes or no, she says, than with the uncharted space in between.
That means science writers have to work hard to coax readers away from those two extremes and toward a more nuanced understanding. “Probability information is crucial to making a really informed decision,” says psychologist Vivianne Visschers, who studies risk communication and decision making at the University of Applied Sciences and Arts Northwestern Switzerland. Without a good understanding of such information, readers may ease up on pandemic social-distancing precautions too early, or avoid a medical examination that they want to have.
There’s no single, straightforward way to write about probability. The very concept can be ambiguous and tricky. But strategies like using analogies, creating visuals, and making careful use of language can help to convey just what a 15 percent chance of an extreme weather event, or an 80 percent chance of recovering from a disease, really means.
