The Abridged Math Tools for Journalists: Wickham Briefing

By Stuart Jones

Chapter 1- Language of Numbers

When using numbers in your articles it is important to know how to write them in AP style. You must spell out single digit numbers, use numerals for multiple digit numbers, unless the number is 1 million or more then round it to the nearest million or tenth of a million. When a number is at the beginnning of the sentence, make sure to spell it out. If a number describing order is one through nine, spell it out but if it is ten or above use the superscript. When using numbers in the story limit how many you use in a paragraph because you don’t want to overwhelm the reader.

Chapter 2- Percentages

The formula for finding a percentage is:

(New figure-old figure)

old figure

Example: new figure = $53,679 old figure = 46,234.

$53,679-$46,234= $7,445

$7,445/$46,234= .161= 16.1%

The salary increased 16.1 percent.

When using percentages in your writing you must spell out the word “percent.” Do not use the symbol % after your percentages. “The price of movie tickets went up seven percent since last year we saw the summer block buster.

Percentage of a whole can be calculated by dividing the part by the whole.

Percentage of a whole = subgroup/whole group. Move the decimal two points to the right.

To convert a fraction to a percentage divide the top number by the bottom number: 13/15 = 0.87

To calculate batting average take the total at-bats and subtract the walks, the sacrifices and the number of times a batter was hit by a pitch. Divide the number of hits the batter made (where he was safe on base) by the previously calculated number.

120 times at bat – 20 walks/sac./hit by pitch = 100 at-bats

40 hits/100 at-bats = .400 batting average

Simple annual interest deals with the principal which is the amount of money borrowed. Money paid for the use of the money is called interest. The rate is the percent charged for the use of money. The amount of money charged depends on the length of time the borrowed money is kept. Interest is calculated in years.

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

Chapter 3- Statistics

The “mean” is also known as the average. If you have a set of number and you want to find the average you add all the numbers of the set together and divide the total by the total number of figures in the set.

Sum of figures/total number of figures in set

The median is the middle number of the set when the numbers are placed in order from least to greatest. If there is an even number of figures in the set, add the two middle numbers together and divide it by two to find the mean. The mode refers to the number appearing most frequently in a distribution of numbers.

Percentile is a good calculation to use when trying to communicate where someone or something stands in comparison to a whole. The formula is as follows:

Percentile rank = (number of people at or below an individual score)/(number of test takers)

Chapter 4- Federal Statistics

Unemployment rate = (unemployed/labor force) x 1000

Practice:

Correct the following use of numbers in this sentence: “10 days ago I found $1,200,000 in my bank account at two hundred thirty-one Eleventh Street.”

Jim Jones, a photographer borrowed $2,000 from the Royal Bank of America to buy a new camer. He agreed to pay 5 percent interest, payable in one payment at the end of the year. What was his interest payment at the end of the year?

Sammy got a 95 on the statistics test she took on Friday. There were 23 other students with that score or lower. There are 30 students in Sammy’s statistics class. What was her percentile rank?

Find the North Carolina’s unemployment rate if there are 200 people unemployed and the labor force is 3,750.

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