Statistical Deception Part 2 We have already looked

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 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 (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 instead of percentages

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. • 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 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” • A confounding variable may be skewing the results.

Ignoring Occam’s Razor

• • • 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 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 Hawaii when Obama ran for office, verified that the birth certificate was genuine.

• 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 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 Barack Obama, Sr. lived in Honolulu at the time Barack Obama, Jr. was born.

• 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”