Become your newsroom’s master of numbers

By Flickr user Kevin Dooley

Percent of total. Margin of error. Mean, median and mode. 

These words could conjure up a college statistics class you desperately tried to avoid. But for journalists who want to assess large amounts of data, a basic knowledge of these computing methods will go a long way. 

In a session called “Necessary Numbers for the Newsroom, ” Jaimi Dowdell of Investigative Reporters and Editors and Jennifer LaFleur of Propublica reviewed some math rules every reporter should master. 

One of my favorites: Adjust money for inflation by checking in with the Consumer Price Index for your area. Make sure you also have a handle on percent change, per capita and margin of error. 

After you get those down, follow Dowdell and LaFleur’s list of what to avoid to ensure your story doesn’t include simple errors: 

1. False accuracy: 12.35 percent of people surveyed said…
2. The superlative of silliness: California has more doctors than any other state. Wisconsin has the most wall-eyed fishing accidents in the country.
3. Saying something is “significant” when you really don’t know or “more likely” without understanding the data.
4. The spurious correlation – saying something correlates when there’s probably something else behind it.
5. Caving into editor’s love of ranking.
6. Ignoring “don’t knows” and non-responses in surveys and polls.
7. Mixing up change and percent change.
8. Confusing percentage points with percentage difference.
9. Not putting numbers into context: “Crime increased 50 percent” but we don’t know what the rate was.

Now that you know what to avoid, here are some Web sites and recommended books from Dowdell and LaFleur’s math tipsheet to help you conquer your number fears: 

• Think you’ve mastered math? Take this test to find out.
• The IRE Resource Center has many tipsheets focusing on math. Search for words like “math or “statistics.”
• “Statistics every writer should know.” In a pinch, this site has some answers to the very basic math questions you may have.
• Dr. Math is not geared toward journalists, but it can be helpful if you need to look up math terms or find more complicated information.
• “Numbers in the Newsroom: Using Math and Statistics in News,” by Sarah Cohen for Investigative Reporters and Editors, Inc.
• “Precision Journalism,” by Philip Meyer.
• “How to Lie with Statistics,” by Darrell Huff and John Allen Paulos.
• “A Mathematician Reads the Newspaper,” by Darrell Huff
  and John Allen Paulos..