1.3 The Power of Data in the Media

Why Study Statistics?

• The media use statistics to inform

• Ideally, information is accurate

• Sometimes can provide misleading or false impressions– On purpose, to sway to public, to increase

ratings/circulation– accidentally

Why Study Statistics?

• To understand how information is represented/misrepresented

• Ability to correctly interpret tables/charts, diagrams, graphs presented in media

How To Lie With Graphs(not an exhaustive list)

• Changing scale on axis

• What impression do these graphs give?

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• What impression does this graph give?

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How To Lie With Graphs(not an exhaustive list)

How To Lie With Graphs(not an exhaustive list)

• Now consider this graph.

• Not starting the graph at 0 can lead to very misleading graphs!

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How To Lie With Graphs(not an exhaustive list)

• Uneven scales • What impression does

this graph give?

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How To Lie With Graphs(not an exhaustive list)

• Improper use of fancy graphics

• Compare the 1st and 3rd quarter

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Let’s go to the handouts!

Other Ways to Lie With Stats: Semi-attached numbers

• Averages: mean, median, or mode?• “Our juicer extracts 26% more juice!”

– 26% more than what?

• Unclear sample size• Sample size too small

– E.g., when Dartmouth College starting admitting women, someone reported that 33.3% of all female students married faculty members!

Be Wary Of…

• Impressively precise numbers– E.g. the average income is $3054.62

• Sometimes the problem is not the data itself• The conclusion drawn from that data could be

faulty• Is the person making the conclusion the author of

the study?• Forecasting future trends based on past behaviour

Misleading or Not?

• A community college claims that 30% of its graduates get jobs that pay a starting salary of $90 000 or more.

• Seems factual, but not enough info given– How recent is the data?– What programs did they graduate from?– In which country did they get jobs?– Starting salary in Canadian dollars?

Misleading or Not?

• 15 % of Canadians do not know who is the current prime minister

• Might be true

• Not enough info about the survey given– Who was interviewed?– Does data include young children or

immigrants?

Misleading or Not?

• Cole got 54% on a recent science test. The class average was 42%. Cole is an above-average science student.

• Just because Cole’s mark was higher than the class average doesn’t imply that he is an above-average science student.

Misleading or Not?

• If you study for over 2 hours for a final exam, you will pass.

• Too many variables missing• Outcome depends on

– Student’s ability in that subject– Difficulty of course– How they study– Etc.

Misleading or Not?

• Eight out of ten people are cured of diabetes if they eat Penelope’s pineapples every day.

• What is the scientific evidence for this claim?

• What is the sample size?• Did they just pick groups of 10 people until

they found one that had 8 who were “cured?”

Misleading or Not?

• 1 in 100 of the U.S. population is in prison

• This is true!

• (1 out of every 100 adults)

• It’s just as important to know when a statistic is true as when it is false

Misleading Conclusions

• Ex: “59% oppose torture: Poll,” Toronto Star, Oct. 19, 2006.

• Poll of 27 000 people in 25 countries

• Note: in US, 36% “okay qualified use,” 58% absolutely opposed it… problem?

The Wall of Bad Stats

• Ways to misuse statistics– Bad graphs– Bad sampling– Bad averages– Bad conclusions– …

The Wall of Bad Stats

• Find bad stats in the media– Print– TV– Radio– Internet

• Bring them in• Short paragraph explaining why they are

bad

The Wall of Bad Stats

• 3 times a year– October, January, March– Different medium each time– Different kind of bad stat each time– Everybody has to bring in a different example – First come, first serve!