Statistical Deception Statistical Deception —Part 2 We have already looked at many ways people lie with statistics:  Bad Graphs  Non-representative samples

. Generalizing to the wrong. population   Generalizing to the wrong population  Comparing apples and oranges  Survey bias – NOYB  Placebo effect  Biased sources  Misuse of the word “significant”  Discounting results as “just statistics”

Other issues can come up in interpreting and publicizing results …

Convenient Averages

•. Choosing the average that. makes you look the best • Choosing the average that makes you look the best (or your opponent look the worst), even if it’s not really a “typical” average • …Is the number they give really “average”?

Assuming everybody is average (or close to it)

• …How spread out are things?

Not adjusting for different sample sizes •. Comparing raw numbers Not adjusting for different sample sizes • Comparing raw numbers instead of percentages

Which is true. . Raw crimes are going up,. mostly because the Which is true?????  Raw crimes are going up, mostly because the country’s population is increasing.  Your risk of being a crime victim has never been lower.

Not adjusting money amounts for inflation

Screwing up the math

• Classic example: Is spinach a high-iron food?

No—in the initial report a decimal point was misplaced. • No—in the initial report a decimal point was misplaced. • Spinach was reported to have 1000 times as much iron as it actually does. • In fact, spinach is pretty much equivalent to any other leafy green vegetable.

Extrapolating from a partial result.

 Does a low-salt diet lower blood pressure?

Sometimes—but mostly not. •. In otherwise healthy. people, there is no Sometimes—but mostly not. • In otherwise healthy people, there is no correlation at all between salt consumption and blood pressure.

• In patients with serious hypertension, reduced salt has been shown to be one of many treatments that may lower blood pressure.

• It doesn’t always work, though—and some patients BP actually increases with less salt consumption. • About seventy years of research have been at best inconclusive.

Assuming cause and effect

•. Remember: correlation. just means “relationship” • • Remember: correlation just means “relationship” • A confounding variable may be skewing the results.

Ignoring Occam’s Razor

•. complex or unbelievable. explanations •. Occam’s Razor says the • complex or unbelievable explanations • Occam’s Razor says the simplest explanation is generally the best. • Always consider the simplest explanation first.

Was there a conspiracy to cover up the fact that President Obama was not born in the United States?

•. Some people have. claimed that the President • Some people have claimed that the President Obama’s birth certificate is fake.

• Many independent experts have examined the birth certificate. They determined the certificate was authentic, had a raised seal, and was of the same format as others issued in Hawaii at the time it was requested.

•. Linda Lingle, a Republican. who was the governor of • Linda Lingle, a Republican who was the governor of Hawaii when Obama ran for office, verified that the birth certificate was genuine.

•. In addition, it has been. noted that birth. announcements were • In addition, it has been noted that birth announcements were published in the Honolulu papers the day after Obama’s birth:

•. A nurse who worked with. the doctor who attended • A nurse who worked with the doctor who attended the birth remembers the doctor commenting on the birth, because having a black father was very unusual in Hawaii at the time.

•. Real estate and tax. records show Stanley. Ann Dunham Obama and • Real estate and tax records show Stanley Ann Dunham Obama and Barack Obama, Sr. lived in Honolulu at the time Barack Obama, Jr. was born.

•. Though some critics still. claim the President is not • Though some critics still claim the President is not a “native-born” American citizen, this claim doesn’t pass Occam’s Razor— which is the reason courts have refused to consider them.

Using a non-standard significance level

 deciding after the fact on a level that guarantees significance

Discounting a result as “just statistics”