Mark Twain

(1835~1910)

There are three kinds of lies.

1. Lies

2. Damned lies

3.Statistics

There are three kinds of lies.

1. Lies

2. Damned lies

3.Statistics

Understand,

“No statistic is perfect.”

People use statistics to persuade us.

How Statistics Are Misused

•Graph

•Bad samples

•Correlation vs. Causality

•Missing data/Error in data

roller-coaster club?

inactive club?

semestervacation

more stable?It can be. But, only one year

sample.

Correlation and Causality

•Arizona is the highest ranked state in respiratory disease death rate.

Estimation: It is because of air pollution in Arizona.

Fact: Many respiratory patients have immigrated to Arizona, which is one of the cleanest states.

About Statistics

naive

critical

cynical

Statistics?

•Who

•Why

•Where

•When

•What

•How

Think critically about

statistics.

Correlation does not imply causality.

•The more firemen fighting a fire, the bigger the fire is observed to be.

Therefore firemen cause an increase in the size of a fire. (x)

Average is not sufficient

•Average Salary

- Company A: $200,000 (100 employees)

- Company B: $150,000 (100 employees)

CEO 99 others

A$10.1 million

$100,000

B$2.13 million

$130,000

•As ice cream sales increase, the rate of drowning deaths increases sharply.

Therefore, ice cream consumption causes drowning. (x)

Correlation does not imply causality.

eyemout

hnose

chin

nose

nose

old woman

eyebrow

mouth

nose

chin

nose

nose

young girl

ear