Note this principle from the beginning:

No number has any meaning unless it is compared with something else.

People have to deal with mathematics every day of their lives. So do journalists.

In fact, the job of the journalist is to present and interpret information for people, and part of the job -- a big part -- is to interpret the numbers that come with that information. No journalist can get away from basic mathematic operations any more than any adult can avoid having to do math in their lives.

If, as a journalism student, you have gone around looking cute but puzzled whenever someone mentions mathematics and thinking, "That's why I majored in journalism -- so I wouldn't have to do math," then here's a word of advice:

Get over it.

• You will need to know basic math to be a good reporter.
  
  
• You must be able to understand how and why figures are calculated.
  
  
• You have to "think mathematically"; that is, you have to be able to reason your way through mathematical information.
  
  
• And, of course, you have to be able to explain this to your audience.

Here are some basic math operations that you should know as a journalist:

Mean or average

An average is a way of getting a picture of a group of numbers. The average tells you something about where the center of the group is. Journalist Bob Niles does a good job of explaining this, so follow the link at the end of the next paragraph.

By Robert Niles: This is one of the more common statistics you will see. And it's easy to compute. All you have to do is add up all the values in a set of data and then divide that sum by the number of values in the dataset. Read more

Median

Averages, however, can be skewed so that they do not always give you the accurate picture of a group of numbers that you need. Sometimes you need to know the median of a group of numbers. Again, follow the link to an explanation by Bob Niles at the end of the next paragraph.

By Robert Niles: Whenever you find yourself writing the words, "the average worker" this, or "the average household" that, you don't want to use the mean to describe those situations. You want a statistic that tells you something about the worker or the household in the middle. That's the median. Read more

Percentage

A percentage is a mathematical means of showing how a part of something related to the whole. All of something is 100 percent. A part of something would be less than 100 percent. Half of the whole is 50 percent.

A percentage is derived by dividing the number representing the part by the number representing the whole. That will produce a number less than one. The percentage is the first two numbers right of the decimal point.

For instance, the population estimate for the United States in 1999 was 272,945,000. Of those, an estimated 33,145,000 lived in California. To find what percentage of citizens lived in California, we would divide the smaller number by the larger one:

33,145,000 / 272,945,000 = .12

We convert that answer to a percentage by moving the decimal point two places to the right.

Thus, we can say that 12 percent of the people in the United States lived in California in 1999.

Percentage of change

Sometimes we want to get an idea of how much something has changed from one point to another. That, too, is often expressed as a percentage. Let?s say that the population of California in 1990 was 29,811,000. How much has it changed from 1990 to 1999? We first subtract the 1990 population figure from the 1999 figure and get 3,334,000. That's how much the state grew in those years, but what was the percentage of change? To find that out we would divide this difference by the 1990 population figure.

3,334,000 / 29,811,000 = ? (figure it out)

Ratios

We encounter ratios every day: miles per gallon, teacher-student ratio, price per pound, the rate of acceptance of freshman applications, etc.

A ratio gives us a way to come one number to another on a rational basis.

A simple ratio can be expressed as a fraction with one number over another, such as 15 / 5. Ratios generally should be reduced as far as possible, and this example can be reduced to 3 / 1.

Ratios can be helpful in giving us a way to compare numbers that may be derived from different bases. For instance, let's say that there were 39 auto fatalities in County A last year, while just to the east in County B, there were 21. You could not rationally compare those two numbers unless the two counties were about the same size or had the same populations. Unlikely.

In fact, County A has a population of 300,000, and County B has a population of 150,000. A way that the National Highway and Traffic Safety Administration uses to compare this kind of data is fatalities per 100,000 population. Consequently, you would divide the population of your county by 100,000 and use that figure to divide the number of fatalities. So, here's what you get:

County A: 39/ (300,000/100,000) = 39/3 = 13

County B: 21/ (150,000/100,000) = 21/1.5 = 14

We can now compare those two numbers (13 and 14) because they both have the same basis -- the 100,0000 population. And we can say that even though there were fewer fatalities in County B than County A, the fatality rate for County B is actually higher.

Do the math

Are you ready for some numbers?

Here's a chance for you to do some math and learn something - in a non-testing situation. Check out this Math Test for Journalists by Steve Doig of Arizona State University. You get problems to solve, a score and then answers and explanations.

And then there is this math exam for journalists from the University of North Carolina. This one has been around for a while, but you will learn a lot from it if you try it.

Chart-based graphics

Chart-based graphics are graphics that present numerical information in a non-text form. These forms are likely to be proportional representations of the numbers themselves. These are what many people refer to when they talk about informational graphics.

Chart-based graphics should exhibit the following characteristics:

Simplicity. Graphics can be complex, but their appearance should be uncluttered. One of the criticisms of many graphics is that they are "chartoons" -- that is, they have too many little figures and drawings that do not add to the reader?s understanding of the information in the graphic. A graphic should contain the minimum items necessary for understanding the information and the maximum items for good appearance.

Consistency. Websites and publications often develop a graphics style just as they adopt a writing style. This style includes rules about what kind of type is used, when color is appropriate, how information is attributed, and a variety of other matters. Like style rules for writing, these rules help both the staff in producing graphics and the reader in understanding them.

Attribution. Information in graphics should be attributed, just as information in news stories should be attributed. As with other information in a publication, sometimes the source is obvious and does not need to be specified. In other cases, attribution is vital to the understanding of a graphic.

Headlines. Oddly enough, one of the most difficult things about producing an informational graphic is writing its headline. Headlines for graphics do not have to follow the rules of headlines for articles; in most publications, they can simply be labels. They need to identify the central idea of the graphic, however, and this is difficult to do in just a few words. One approach many graphic journalists use to writing a headline for a graphic is to write it before the graphic is built. Doing that gives them the central idea to keep in mind while producing the graphic.

Types of charts that present numerical data

Most mass media publications use three types of chart-based graphics: the bar chart, the line chart, and the pie chart. (There are other types of charts for presenting numerical information such as the scattergraph, but these are not commonly found in the mass media.) Each type of chart is best used for presenting certain types of information and is inappropriate for other types of information. Editors need to understand what charts are appropriate for what types of information.

Bar charts. The bar chart is the most popular type of chart because it is easy to set up, and it can be used in many ways. The bar chart uses thick lines or rectangles to present its information. These rectangles represent the amounts or values in the data presented in the chart. (There are technically two types of bar charts. One uses the name bar chart and refers to charts in which the bars run horizontally. The column chart refers to bar charts in which the bars run vertically. Column charts are more commonly used when time is an element in the data, but that is not a strict rule.)

The two major lines in a bar chart are the horizontal axis, known as the x-axis, and the vertical axis, known as the y-axis. Both should have clearly defined starting points so that the information in the chart is not distorted, particularly the axis that represents the amounts in the graph.

One of the reasons a bar chart is so popular is that it can show both amounts and relationships. It can also show a change in amounts and relationships over time. The chart above demonstrates the bar chart's ability to show relationships, particularly when there is a large amount of data. From a brief look at this chart, the reader knows how these colleges compare to one another as well as something about each school.

So, here's what important about a bar chart:

• A bar chart is good for showing a single set of data, or -- to a limited extent -- multiple sets of data.
  
  
• A bar chart allows you to compare pieces or sets of data easily.

Line charts. Whereas the bar chart may show change over time, the line chart must show change over time. It can also show a change in relationships over time. In some instances, it is preferable to the bar chart because it is cleaner and easier to decipher.

The line chart uses a line or set of lines to represent amounts or values, and the x-axis represents time. One of the standard conventions of the line chart is that the x-axis represents the time element and the y-axis represents the amounts or quantities being represented.

Line charts can use more than one line to show not only how one item has changed but the relationship of changes of several items. Data points can be represented by different shapes for each item. The danger with multiple line charts is that too many lines can be confusing to the reader. Graphic journalists should avoid putting more than three lines in a line chart.

Here's what's important about line charts:

• A line chart shows change over time.
  
  
• Data amounts are always shown on the Y-axis (vertical).
  
  
• Time is always shown on the X-axis (horizontal).
  
  
• Any use of a line chart to show something other than change over time is incorrect.
  

Pie charts. The pie chart is another popular means of showing data, but its use is specialized. A pie chart should show how an entity or item is divided up, and the divisions are most commonly expressed in percentages that add up to 100 percent. Figures also may be used to identify the parts of a pie chart, but it is important that the creator of a pie chart keep the concept of percentages in mind.

Despite the strict limits of the kind of data that can be shown in a pie chart, this type of chart can be used in a variety of ways. A pie chart can show only one set of data at a time, but several charts can be used together to help compare sets of data.

Here's what's important about pie charts:

• A pie chart should be use only to show parts of a whole.
  
  
• Time is not an element in pie chart data.
  
  
• Data in a pie chart are usually expressed as percentages, and those percentages must add up to 100.

If you are really interested in charts and graphs and in displaying numerical information correctly, you should take a look at the books of Edward Tufte, beginning with The Visual Display of Quantitative Information. They are amazing and absorbing books that are beautifully designed and produced.

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Weekly news quiz

You can find some of the quiz questions that might be asked in lecture here.