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Misuses of Statistics

Misuses of Statistics. Voluntary response sample (self-selected) Internet, call-in, magazine polls Small samples “4 out of 5 dentists prefer…” Self-Interest Study Company-sponsored studies Precise Numbers “People spent an average of $23.12 on a gift”. Questions. Loaded questions

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Misuses of Statistics

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  1. Misuses of Statistics • Voluntary response sample (self-selected) Internet, call-in, magazine polls • Small samples “4 out of 5 dentists prefer…” • Self-Interest Study Company-sponsored studies • Precise Numbers “People spent an average of $23.12 on a gift”

  2. Questions • Loaded questions • Order of questions • Refusals (non-response)

  3. Misleading Graphs

  4. Worker Salary $2000/mo Manager Salary $4000/mo Misleading Pictographs

  5. Percentages • Percentage has to be of something • 100% means all of it • Percents are based on a “base” amount 10% extra savings on clearance merchandise (50% off). $100 coat -> $50 clearance price 10% extra -> $45 final, not $40

  6. Correlation and Causation • Just because two things have a relationship does NOT mean one causes the other. • Even when a causal relationship is likely, we have to be careful about assuming what is the cause, and what is the effect. Golf scores and salary for CEOs Prozac and Suicide risk

  7. Homework 1-3: 3, 5, 11, 17

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