Some Statistical Antics in the Media

Arnold Barnett, MIT

Correlation is Not Always Causality. It Is Sometimes Nothing.

“Why Music Matters”“Kids who study music get higher scores on their SATs. … Music helps to improve overall academic performance.”

--Parade Magazine, 12/28/03

"I know from experience that everyone who taught Statistics got a lower (student) evaluation than those who taught courses that are a little less challenging.”

--John Antel, Provost, University of Houston

(quoted in WSJ 10/23/10)

This week, a student sent me an “analysis” that argued that having a passport reduces the risk of diabetes.

Anything wrong with this?

Some Comparisons Can Be Intensely Misleading

The New York Times Identifies 2003’s “Top Summer Movies”

Movie Release Date1. Finding Nemo May 302. The Matrix Reloaded May 153. Pirates of the Caribbean July 94. Bruce Almighty May 235. X2: X-Men United May 2

The rankings were based on “box office receipts, May 2 to August 24, 2003” (!!!!!)

“Oscar likes films with concise titles”

-- TIME, 2000

TIME based this conclusion on its study of best-picture winners over the previous 20 years.

Really? Some Data about Title Lengths

TIME’s Winners All US Movies

Mean 2.3 Words 2.6 words

Median 2.5 words 2.0 words

Some Data Analyses Make Little Sense

“Will US Do Enough to Identify Potential Terrorists, or Will It Go Too Far?”

57% 45%

Won’t Do Enough

Will Go Too Far

Whites Blacks

“Only once in its 107-year history has the Dow Jones Industrial Average suffered a lower close four years in a row. So …..the odds against it happening this year are something like 104-to-1.”

---Barron’s, 1/3/03

Of course, the Dow Jones can only decline for a fourth year in a row when it has declined the previous three years.

N’est ce pas?

That circumstance had only arisen in three years: 1904, 1932, and 1942. In one of these years (namely, 1932) the Dow Jones declined yet again.

Proper estimate: 1 in 3?

In April 2010, The New York Times informed us of “the best places” to hail a cab in Manhattan.

Its computer analysis of 90 million rides identified the places where the largest numbers of people had started their taxi rides.

But the number of people who caught cabs at spot X is not the same as the percentage of people who sought cabs at X and actually got them.

And isn’t the percentage the appropriate metric for passenger success?

Bad Data Can Kill

A statistical expert testifying in 2000 for Vice-President Gore stated that the Florida punch-card ballot was defective on its left side.

As evidence, he noted a 1998 election in Palm Beach County, in which there were 3% fewer votes recorded in the race for Senator (left side of the ballot) than for Governor (right side).

The opposing attorney asked whether the witness had ever examined the 1998 Palm Beach ballot. Had he done so, the lawyer said, he would have realized that the Senate and Governor’s races were both on the left side of the ballot.

Thus, the statistician’s left/right comparison was preposterous.

(The statistician looked pale.)