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Transcript of News & Numbers 2009. Why should journalists know numbers & math? ·Explain what numbers mean to...

• News & Numbers2009

• Why should journalists know numbers & math?Explain what numbers mean to readers

Make complicated numbers understandableCreate impact in storiesGive context to a situation

Check credibility of government, industry, etc.Do the numbers back up what theyre saying? What are the numbers hiding?

• Editing with numbersBalance!Too few numbers unclearToo many numbers confusing

Context!Be careful when comparing raw numbers

Accuracy!Know how to apply & check formulas

• Finding numbers & statisticswww.fedstats.govwww.census.govhttp://ucblibraries.colorado.eduInterview the Web siteLook at domain names: .gov, .edu, .orgCheck for professional layout, spelling, grammar, etc.Check site informationAP conducts several surveys and polls: http://surveys.ap.org/The National Council on Public Polls suggests journalists consider several questions before accepting poll or survey data: http://www.ncpp.org/?q=node/4Cornell University provides great analysis tips for polls: http://www.library.cornell.edu/olinuris/ref/pollres.html

• Using data in articlesIn articles, poll/survey data is typically presented in percentages. According the AP Style handbook, percent is always written as one word. One should use figures for percent and percentages: 1 percent, 2.5 percent (use decimals, not fractions), 10 percent, 4 percentage points. For a range, 12 to 15 percent or between 12 and 15 percent. For amounts less than 1 percent, precede the decimal with a zero: The cost of living rose 0.6 percent.

• Key FormulasPercent of totalAmount/total * 100In 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 formulasPercent changeDifference / Original * 100Undergraduate 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 pointWhen comparing raw numbers, use percent change

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

• Key formulasPer capitaNumber of occurrences/Total populationIn 2005 Boulder had 551 burglaries and L.A. had 21,543 burglaries. Does this mean youre less likely to get burglarized in Boulder? Not quiteBoulders 2005 population: 102,659L.A.s 2005 population: 3,731,437Whats the per capita burglary rate?Boulder = 551/102,659 = 0.005L.A. = 21,543/3,731,437 = 0.006

• Key formulasPer 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 sense0.005 * 1000 = 5Boulder has about 5 burglaries per 1000 people

• Key formulasEstimating crowd sizeAdds context and descriptive power when talking about an event

Square footage of venue/density of crowd

Rules of thumb:Densely packed crowd: 2.5 square feet per personModerately dense crowd: 5 square feet per personLoosely packed crowd: 10 square feet per personPay attention to units and conversion factors!

• Mean, Median and Mode

• StatisticsAVERAGE??? Be careful with this word!Mean=statistical averageSum of all values/number of valuesCEO 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

• StatisticsMedianThe value in the middle\$100,000; \$50,000; \$25,000; \$15,000; \$10,000Median = \$25,000Often a better reflection of the range of valuesCautions:Mean can be skewed by whats happening at the outer boundaries, but median might not reflect changes happening in the high or low range

• Polls and SurveysPollestimate of public opinion on a single topicWhich candidate will win the election?

Surveymultiple questions asked to get data about a sample of the populationAmerican Community Survey (U.S. Census)

• Poll/Survey Sourceswww.pollingreport.com (multiple sources)www.gallup.com (Gallup polls)www.ciruli.com (polls and analysis from a Colorado company)http://ucblibraries.colorado.eduBrowse research & subject guide for P-Polls or Public Opinion Information

• 5 Ws of describing pollsWHO is behind the pollWHAT is being polled (slight changes in wording can affect response)WHEN was the poll takenWHERE did the sample come from (nationwide vs. Colorado)HOW was the poll conducted (random vs. targeted, phone vs. Internet)

• PollsMargin of ErrorMaximum distance from the expressed value that the true result should beExpressed as +/- %47 percent polled said theyd vote for Clinton, with a margin of error of + 4%The actual result should be from 43-51 %Sample size affects Margin of Error400 people, margin of error ~ 5 %1000 people, margin of error ~ 3 %

• PollsConfidence levelThe likelihood the actual result will fall within the margin of errorSet by pollsters ahead of time, usually 95 %The other 5 percent of time, the result could be way outside the margin of errorA lower confidence level gives a smaller margin of error, but means greater likelihood the actual result could be way off.

• PollsAlways include margin of error when writing poll results in a story!Political pollsoften very close, margin of error can cancel out any apparent lead

• Example 1Q: 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 2Q: 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 Brits salary decreased by 48 percent.

• Example 3Q: 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 plazafirst convert yards to ft, 1 yard = 3 feet so...300 * 3 and 600 * 3 = 900 ft by 1800 ft900* 1800 = 1,620,000 square feet1,620,000 sq. ft / 10 sq. ft/person = 162,000 people

• Example 4Q: 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 5Q: 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 6Q: 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 7Q: 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 = \$492.6Whats the median salary?= \$560

• Questions??http://www.ire.org/education/math_test.htmlLink 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

*These sites are resources to use to find numbers. The fed stats site is great because it is a clearing house for all kinds of info. Including but not limited too census data. The University Library here at CU also provides a list of a bunch of different databases where you can access statistical information.