Data journalists Jennifer LaFleur and Jaimi Dowdell offer tips on presenting numbers correctly

Notorious mistakes that investigative reporters make with numbers include trying to calculate percentages by adding or subtracting from other percentage values.

Confusing correlation with causation is another major category error.

Even technically accurate numbers can also mislead or confuse readers due to inappropriate formats, too many digits in the copy.

A common misunderstanding about the meaning of “per capita” simply means per capita.

Use graphics when numbers don’t show the scale.

Be careful with billions , and show scale, experts say.

Read your draft aloud, and ask: “What have I forgotten?”.

Experts urge reporters to “choose your numbers as carefully as you choose your quotes” and limit the total number of digits mentioned in any paragraph to eight or fewer.

Avoid averaging averages, and use a simple method to calculate “ one out of” risk probabilities.