Weather Underground (or "Wunderground") recently launched a campaign to tout their top-of-the-heap forecast accuracy compared other private weather companies. And in classic marketing form, they distorted the hell out of the graph to drive home their point.
Under a section called "We Are Smarter," Wunderground — which is owned by The Weather Channel and whose forecasts operate autonomously from its parent company — provides a chart showing how much more accurate their weather forecasts are compared to other private forecasting companies, including The Weather Channel, WeatherBug, and AccuWeather. The chart uses forecast accuracy ratings measured by ForecastWatch for nearly 800 cities across the United States between May and July of this year.
Wunderground scores the highest marks across the United States during the three-month period with a 77.12% accuracy rate. The lowest rated is a company called "MyForecast," pulling 70.73%. Relatively speaking, that's not much of a difference, but you certainly wouldn't think that after looking at this chart.
While the data itself isn't questionable, its visual presentation on the graph is intentionally misleading. Even though 6.39% separates the lowest rated from the highest rated, the bar for Wunderground is nearly ten times longer than the forecasting outlet that comes in last on the graph. The company snipped the x-axis to range from 70% to 80% in order to make Wunderground look exponentially more accurate than its competitors.
If the company had used any range other than 70% to 80%, the difference between Weather Underground and its six other competitors would look negligible.
These tactics are among the first lessons taught in Introduction to Statistics courses in college, as people and companies frequently skew graphs to trick viewers into thinking there's more (or less) of a discrepancy so they side with the argument being made.
The Vane reached out to The Weather Channel for comment, and a spokesperson confirmed that the graph is part of "a marketing campaign using research to prove a point," and that the graphic is used to highlight the difference in accuracy between forecasting outlets. The spokesperson also mentioned that the 6.39% difference is "statistically significant" given the data points that ForecastWatch uses to arrive at its accuracy numbers.
The most common place for the public to see graphical exaggeration is on Fox News. Admittedly, the news network draws-up questionable graphs for political purposes rather than to make themselves look better than their competitors, but it's a great study in using charts to misrepresent data. For example, here's a screenshot from their Obamacare coverage last March:
And for the unemployment rate in 2011:
And during coverage of the Bush tax cuts:
Back at the beginning of May, I contributed to a project spearheaded by Deadspin's former data guru Reuben Fischer-Baum to determine which forecasting outlet is the most accurate. Using data from a different accuracy tracker called ForecastAdvisor, we found that The Weather Channel blew its competition — NWS, AccuWeather, and Custom Weather (MyForecast) — out of the water. Weather Underground also does exceptionally well, but their data on ForecastAdvisor was too scattered to use it nationwide.