Math Tools for Journalists – Analysis of Chapters 1-4

By Kellye Coleman

Journalists must rely on numbers.

Whether writing about last night’s basketball game, changes that will affect property taxes or the percentage increase of burglaries in town, journalists have to know how to handle numbers and present them clearly.

Although it is sometimes tempting to exclude numbers whenever possible, journalists have the responsibility to provide their readers with clear, accurate information and data.

Most of the math skills journalists need are basic, and tips for dealing with the language of numbers, percentages, statistics and federal statistics are explained below.

The Language of Numbers

“Interview the numbers with the same care that you interview people.”

– Math Tools for Journalists

It is critical that journalists check the math of official reports and speakers before publishing a story. Sometimes numbers have been tweaked to look better or the individual presenting them lacked basic math skills.

Also, just as important to consider the words that will accompany any numbers presented, for two reasons. First, readers must be able to understand what is being said, so the language a journalist uses needs to be clear and concise. Second, the use of a particular word can change the impact the number has, such as using more versus most.

Graphic by Kellye Coleman


“Reporters frequently are faced with figures that could be more clearly explained if they were converted to percentages. By accurately calculating the percentages, the reporter is helping the reader better grasp the issue.”

– Math Tools for Journalists

Percentages are used to show increases, decreases, percentage points and percentage of a whole.

Percentage increase and decrease can be found using a simple formula:

Percentage inc./dec. = (new figure – old figure) ÷ old figure

*Convert to percentage by moving decimal two places to right.

This formula can be used to calculate percentage increase and decrease, but the answer for percentage decrease will have a negative sign in front of it.

Calculating the percentage of a whole provides readers with perspective and can also be found through a simple formula.

Percentage of a whole = subgroup ÷ whole group

*Move decimal point two places to right.

It is important to understand the difference between a percentage and percentage points. One percent is one-hundredth of something, but one percentage point may also be something different than one-hundredth of a percent.

Percentages are often used for calculating interest. Money that is borrowed is referred to as the principal, while the interest is the money paid for the use of money.

In order to calculate interest, use the following formula:

Interest = principal x rate (as a decimal) x time (in years) 


“Having a basic understanding of statistics and the role played by the manipulation of numbers is an important elements in a journalist’s toolbox.”

– Math Tools for Journalists

Journalists also commonly use statistics, particularly when analyzing surveys and studies and providing readers with numbers that are clear and accurate. This is particularly important, because stats are easy to present in ways that can make them look a certain way.

Example Problems

To understand statistics, journalists must understand several key pieces – mean, median, mode.

The mean, often referred to as “the average,” is the sum of all figures in a group divided by the total number of figures. The median is the midpoint of a group of numbers. The mode is the number that appears most often within the grouping of numbers.

An understanding of percentiles is also important. A percentile score is the number that represents the percentage of scores that at or below that designated score. The formula for determining a percentile score is:

Percentile rank = (# of people at or below an individual score) ÷ (# of test takers)

Finally, it is common to find standard deviation figures in scientific documents or investment reports. A standard deviation figure how much a particular group varies from the norm. Oftentimes, this is displayed on a bell curve, with the highest point of the curve representing the mean. To calculate a standard deviation:

  1. Subtract the mean from each score
  2. Square the resulting number for each score
  3. Compute the mean for these numbers (this figure called the variance)
  4. Find the square root of the variance 
Federal Statistics

Data and information is constantly made available by the government, and it is incredibly important for journalists to know where the info is coming from and how it impacts people. Reporters are often writing stories about inflation and consumer price index, gross consumer product and trade balance, but the one focused on in this section is unemployment rate.

Understanding unemployment rate is incredibly important, particularly in a time when many are struggling. The formula for calculating unemployment is:

Unemployment Rate = (unemployment ÷ labor force) x 100

The labor force is everyone 16 and older who has a job or is currently seeking a job. The unemployment rate is the result of a survey of 60,000 households that is taken each month. One is employed if they have worked in the week before the survey was taken.

An understanding of percentages, statistics and federal statistics are extremely important tools for journalists to have. Paying attention to these areas will allow for journalists to complete accurate reporting and writing.


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