News & Numbers

2009

Why should journalists know numbers & math?

· Explain what numbers mean to readers

· Make complicated numbers understandable• Create impact in stories• Give context to a situation

· Check credibility of government, industry, etc.· Do the numbers back up what they’re saying? · What are the numbers hiding?

Editing with numbers

· Balance!· Too few numbers unclear· Too many numbers confusing

· Context!· Be careful when comparing raw numbers

· Accuracy!· Know how to apply & check formulas

Finding numbers & statistics

• www.fedstats.gov

• www.census.gov: The census website

• http://people-press.org/: PEW polls

• http://surveys.ap.org/: surveys and Polls from AP

Checking Accuracy

• “Interview” the Web site

• The National Council on Public Polls suggests journalists consider several questions before accepting poll or survey data: http://www.ncpp.org/?q=node/4

• Cornell University provides great analysis tips for polls: http://www.library.cornell.edu/olinuris/ref/pollres.html

AP style for percentage

• Use figures (e.g. 2, not two)

• Use decimals, not fractions (e.g. 2.5 percent, not 2 ½ percent)

• For range use 12 to 15 percent or between 12 and 15 percent

• For amounts less than zero precede the decimal with a zero (e.g. 0.6 percent not .6 percent)

Key Formulas: Percent of a total

· Percent of total· Amount/total * 100

· In 2007, CU had a budget revenue of $904 million, of which $396 million came from student tuition and fees. What percentage of the budget revenue comes from tuition & fees?

· 396/904 * 100= 43.8 percent

Key formulas: Percent Change

· Percent change· Difference / Original * 100

· Undergraduate resident tuition in the J-school was $5,628 for the 2007-08 academic year and $4,734 for the 2006-2007 academic year. What is the percentage change?

· Difference(5628-4734)/Original(4734) * 100%= 18.9 % increase!

Percent vs. percentage point

· When comparing raw numbers, use percent change

· BUT, when comparing two different percent values (e.g. polls) talk about percentage point change· Going from 50 percent to 60 percent is a 10

percentage point increase.

Key formulas: Per Capita

· Per capita· Number of occurrences/Total population

· In 2005 Boulder had 551 burglaries and L.A. had 21,543 burglaries. Does this mean you’re less likely to get burglarized in Boulder? Not quite…

· Boulder’s 2005 population: 102,659

· L.A.’s 2005 population: 3,731,437

· What’s the per capita burglary rate?· Boulder = 551/102,659 = 0.005

· L.A. = 21,543/3,731,437 = 0.006

Key formulas: Per Capita

· Per capita, cont.· Boulder and L.A. have similar per capita

burglary rates. But would you report that value in a story?

· Multiply per capita amount by a factor that makes more sense

· 0.005 * 1000 = 5

· Boulder has about 5 burglaries per 1000 people

Key formulas

· Estimating crowd size· Adds context and descriptive power when talking

about an event

· Square footage of venue/density of crowd

Crowd size rules of thumb

· Densely packed crowd: 2.5 square feet per person

· Moderately dense crowd: 5 square feet per person

· Loosely packed crowd: 10 square feet per person

· Pay attention to units and conversion factors!

Mean, Median and Mode

· http://www.youtube.com/watch?v=uydzT_WiRz4

· Mean/Average: Add all the numbers in the data set together and divide by the number of numbers in the data set. Confused? See below· Data set: 5, 2, 5, 6, 7· Total: 5+2+5+6+7=25· Mean/Average: 25/5=5 

Median

Mode

· Mode: The number that appears most often in a data set. If no number repeats, there is no mode. There can be multiple modes.· Data set: 5, 2, 5, 6, 7· Number that appears most: 5

Statistics

AVERAGE??? Be careful with this word!· Mean=statistical average

· Sum of all values/number of values· CEO makes $100,000/year, manager makes $50,000/year,

administrative assistant makes $25,000/year, factory worker makes $15,000/year, intern makes $10,000/year. What is the average salary?

· (100,000 + 50,000 + 25,000 + 15,000 + 10,000)/5

· $40,000

Statistics

· Median· The value in the middle

· $100,000; $50,000; $25,000; $15,000; $10,000· Median = $25,000· Often a better reflection of the range of values

· Cautions:· Mean can be skewed by what’s happening at the

outer boundaries, but median might not reflect changes happening in the high or low range

Polls and Surveys

· Poll—estimate of public opinion on a single topic· Which candidate will win the election?

· Survey—multiple questions asked to get data about a sample of the population· American Community Survey (U.S. Census)

Poll/Survey Sources

· www.pollingreport.com (multiple sources)· www.gallup.com (Gallup polls)· www.ciruli.com (polls and analysis from a

Colorado company)· http://ucblibraries.colorado.edu

· Browse research & subject guide for P-Polls or Public Opinion Information

http://people-press.org/ PEW polls

5 W’s of describing polls

· WHO is behind the poll· WHAT is being polled (slight changes in

wording can affect response)· WHEN was the poll taken· WHERE did the sample come from

(nationwide vs. Colorado)· HOW was the poll conducted (random

vs. targeted, phone vs. Internet)

Polls

· Margin of Error· Maximum distance from the expressed value that

the true result should be

· Expressed as +/- %

· 47 percent polled said they’d vote for Clinton, with a margin of error of + 4%

· The actual result should be from 43-51 %

Polls

· Confidence level· The likelihood the actual result will fall

within the margin of error· Set by pollsters ahead of time, usually 95 %· The other 5 percent of time, the result could

be way outside the margin of error· A lower confidence level gives a smaller

margin of error, but means greater likelihood the actual result could be way off.

Polls

· Always include margin of error when writing poll results in a story!

· Political polls—often very close, margin of error can cancel out any apparent lead

Example 1

· Q: Last year's city budget was $7,000,012. This year, you're told, the budget will be cut by 5 percent. What will this year's budget be?

· A: $7,000,012 * 0.05 = $350,000.60 $7,000,012 - $350,000.60 = $6,650,011.4

Example 2

· Q: Britney Spears salary was cut from $12.6 million to $6.5 million. Gasp!What was the percent change?

· A: 12.6 million – 6.5 million = -6.1 mil.(- 6.1million/12.6 million )* 100 = - 48.4 %

The Brit’s salary decreased by 48 percent.

Example 3

· Q: In a loose crowd, each person takes up about 10 square feet. What is the best estimate of how many people gathered to see a chicken wings eating contest that loosely fills a city park measuring 300 yards by 600 yards?

· A: Area of plaza—first convert yards to ft, 1 yard = 3 feet so...· 300 * 3 and 600 * 3 = 900 ft by 1800 ft· 900* 1800 = 1,620,000 square feet· 1,620,000 sq. ft / 10 sq. ft/person = 162,000 people

Example 4

· Q: Your city of 200,000 had a total of 68 murders last year. What was the murder rate per 100,000?

· A: Per capita rate = 68/200,000=.00034 0.00034 * 100,000 = 34

Example 5

· Q: Students at a CU football game drink about 300,000 gallons of lemonade. You want to make that volume relevant to your readers by saying how many backyard swimming pools (which hold about 12,000 gallons) it would take to hold that much lemonade. About how many swimming pools would the lemonade fill?

· A: 300,000 gallons / 12,000 gallons~ 25 swimming pools

Example 6

· Q: Last year coffee shops on the Hill has had two armed robberies. This year: none. How would you describe the change?

· A: 0 – 2 = -2-2 / 2 * 100% = -100 %

A 100 % decrease in murders

Example 7

· Q: The interns at five different magazines in Boulder are paid $3, $100, $560, $800 and $1,000 a semester. What is their average salary?

· A: (3+100+560+800+1,000)/5 = $492.6

· What’s the median salary?= $560

Questions??

http://www.ire.org/education/math_test.html

Link to these questions and a few more to practice

http://www.robertniles.com/stats/

Helpful site with good def.

http://www.cnn.com/2004/ALLPOLITICS/09/27/polls.explainer/ This site explains margin of error and what it means in terms of political candidate polls. It also explains the basics of how polling is done in America