Math 4 Journalists

Newsroom Math Using what you learned in 6 th grade www.CubReporters.org

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“ If I wanted to do math, I wouldn’t have majored in journalism!”
As a journalism professor, I hear this often. Most journalists would rather craft words than crunch numbers. But many stories require numbers. There are news stories about salaries, budgets, test scores, surveys, political polls, census data, etc. And nearly all sports stories involve numbers. So not only do journalists need to be good writers, they also need some math skills. This slideshow tutorial will cover the basics.
Mark Grabowski Journalism Professor Marist College

Percentage change
Use this formula:
(New – Old) /Old … then x 100
For example: Last year’s ticket sales brought in $1,000. This year’s ticket sales brought in $1,250. What was the percentage change?
1250-1000 = 250
250/1000 = .25
.25 x 100 = 25%

Percentage change
The International Club’s budget was cut last year from $2,000 to $1,000. What was the percentage change?
1000 – 2000 = - 1000
-1000/2000 = -.5
-.5 x 100 = - 50%

Percentage change
Last year, the city had 3 homicides.
This year there were 0.
What was the percentage change?
0-3 = - 3
-3/3= - 1
-1 x 100 = - 100%

Percentage change
Last year’s sorority budget was $12,000.
This year, there will be a 10% cut.
Next year, there will be a 10% increase.
What will the new budget be this year?
Will we be back to normal NEXT year?

Percentage change
A 10% decrease is a change of -.10
12000 x - .10 = - 1200
12000 – 1200 = 10,800 this year
A 10% increase is a change of +.10
10800 x .10 = 1080
10800 + 1080 = 11,880 next year

Percentage change
Be careful! A 200 percent increase is not the same as “double.” It’s a 100 percent increase that is actually the figure that is twice the size of the previous number. A 200 percent increase is triple the original.

Rate per thousands …
When calculating percent, we multiply by 100 because that’s what percent means: per 100.
If calculating a rate per 1,000 people or per 10,000 people, we multiply by THAT number.

Rate per thousands
Your city of 350,000 had 70 murders last year. What was the murder rate per 100,000?
70/350,000 = .0002
.0002 x 100,000 = 20
This way different cities’ rates can be compared.

Crowd counts
Handy rule: In a loose crowd, each person takes up about 10 square feet.
How many people are at a protest demonstration that loosely fills a city square that measures 50 yards on each side?
50 yards = 150 feet.
150 x 150 = 22,500 square feet
22,500/10 = 2,250 protesters

Crowd counts
Handy rule: In a tight crowd, each person takes up about 7.5 square feet.
The basketball team came home to a cheering crowd in an airport space about 75 x 20 feet. How many were there?
75 x 20 = 1500 square feet.
1500 / 7.5 = 200 people cheering

Mean v. Median
A mean is an average .
If your quiz scores are …
9, 8, 6, 8, 4
… then your average is
(9 + 8 + 6 + 8 + 4)/5 = 7

Mean v. Median
A median is a midpoint.
Your median quiz score would be …
9
8
8
6
4

Mean v. Median
This difference can be important in news stories.
“The average salary of a Marist College graduate in Public Relations is $100,000.”
… true statement!

Mean v. Median
The explanation goes something like this:
Anjali Agarwal $ 10,000
Ben Billman 20,000
Cathy Clark 22,500
Dave Dawson 25,000
Rick Smits 422,500
$500,000
500,000/5 = $100,000 each!
… But what’s the median ?

Rounding numbers
It’s OK to round off large numbers in your stories. For example, you can use 1.4 million instead of 1,421,317. But be careful rounding to just two digits – rounding 1,562,000 up to 1.6 million leaves out almost 40,000 of whatever. That’s a pretty significant amount. So, it may be more accurate to round down to 1.56 million

How to Write Numbers
The AP Stylebook ’s general rule is to spell out numbers from zero through nine and use numerals for numbers 10 and above. If it has two digits or more, make it a number!
Some exceptions are millions, percentages, ages, years, headlines – always use numbers for these.
Note that you spell out “percent,” “feet,” “inches,” “yards,” etc. in stories.
There are references to numbers throughout the AP Stylebook , but many of the commonly-used figures are under the ‘dimensions’ entry.

For more tips and practice…
Visit http://CubReporters.org/math
E-mail mark@cubreporters.org
Questions?

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Math 4 Journalists

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