To calculate a percentage of whole, add all the values in the collection. Percent of whole: When you are describing how much one value among a collection of values contributes to the entire collection, a percentage of whole is a good place to start. To calculate the percent change, subtract the initial value from the changed value, divide by the initial value, and then multiply that value by 100. Percent change: To help readers understand the difference in a changing set of numbers, such as time or price, a percent change can be helpful. Multiply this figure by 100 to get a percentage: 3.95%. For example, to determine what percentage 62 among 1,567 total is: 62 / 1567 = 0.0395. It is calculated by multiplying the numerical value by 100.įinding a percentage: To calculate what percentage a number is of another larger number, divide the former by the latter. A percentage is a fraction of a whole, or of 100. In news stories with raw numbers, percentages are often helpful to describe the data to readers in a meaningful way. For example, in the numbers 300, 400, 500, 400, 200 and 400, 400 is the mode - it occurs three times in a group of six numbers. The mode is the most reoccurring value in a collection.
However, it can be helpful in determining a pattern of reoccurrence. Mode: Used less frequently in journalism than in statistics, the mode is more of an indicator than an accurate measurement.
If the collection is an even number of values, take the two values in the middle and calculate their mean by adding them together and dividing by two. For example, the median of 50, 300, 400, 500 and 5,000 is 400 - the value in the center of the list of values. If the number of values being examined is odd (3, 11, 131, etc.), the value directly in the middle is the median. To find the median of a collection of values, sort the values in descending order. Median: If there is an extremely high or low value in a collection of values - say, one person with a high income in a group of low-income residents - the median is often a more accurate way to measure the central tendency of the group of numbers. The mean is a good tool when all the values are relatively close in amount to show the "central tendency." If most of the values are similar and one value is much higher or lower, the mean will not be a precise estimate of the commonality. Divide this by three (the number of values we're looking at), and the result is 400 - the mean. It is calculated by dividing the sum of values in a collection by the number of values. Mean: The mean is known more commonly as an average. The three mathematical concepts - "mean," "median" and "mode" - are often lumped into the colloquial term "average." All three measure different things, however, and using them interchangeably or in the wrong context can result in an incorrect story. If you'd like to dig deeper, a good place to start is "News and Numbers: A Guide to Reporting Statistical Claims and Controversies in Health and Other Fields." Here are a few basic concepts to keep in mind when number-crunching for a story. And, most important, you should be able to use this knowledge to help your readers better understand the issues at hand.
You should also understand what margin of error in polling is, have a basic understanding of probability and be able to work with graphs and charts. You should have a working knowledge of arithmetic, be comfortable with statistics and be able to calculate percentages, ratios and other relationships between numbers. Truly understanding numbers and being able to clearly convey their meaning to readers is a crucial part of being a journalist. It can even tell you when something is fact or folly. But sidestepping or downplaying numbers can be perilous.Īppropriately and accurately used, they can be the very foundation of a story - a project is over or under budget students' graduation rates are above or below average prices are collapsing or spiking. Journalists are often thought of as being "word people," and however true that may or may not be, even the most diligent reporter can blanche when faced with a thicket of figures. JMath basics for journalists: Working with averages and percentagesīy Leighton Walter Kille, The Journalist's Resource June 15, 2014 Math basics for journalists: Working with averages and percentagesīy Leighton Walter Kille, The Journalist's Resource
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