CO SCI 58
Asking the Right Questions
Statistics are evidence expressed as
Often just educated guesses or estimates because of
difficulties in collecting data
Lack of truthfulness
Failure to report events
Physical barriers to observing events
Clues for Evaluating Statistics
1. How were the statistics obtained?
2. What type of calculation was used?
3. Do the statistics prove the conclusion or something
4. Compare the necessary statistical evidence with what
is actually provided.
5. Form your own conclusion from the statistics and ask
“Is there missing information?”
There are three different calculations that might be
called an “average”:
Mean: Add all of the values and divide the total by the
number of values
Median: List all of the values from highest to lowest and
find the one in the middle
Mode: Find the value that appears most frequently
An Average is an Average?
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“averages”? Mean 1,069,274
Mode None (no repeats)
Pay close attention to the wording of the statistics and the
wording of the conclusion to see whether they are
referring to the same thing.
The financial problems of our public schools are highly
overrated. In 1992-93, an average $6,100 was spent on every
public school student in the United States. Furthermore,
full-time public school teachers make an average $34,027
per year according to the American Federation of Teachers.
This salary is not at all bad, compared to the 1990 median
income of $34,400 of families in the U. S.. It isn’t
insufficient funding or ill-paid teachers that are killing the
educational system; it is, instead, the lack of well-trained
teachers thanks to grossly lax colleges of education.
The conclusion is:
The educational system is being killed by the lack of well-
trained teachers thanks to grossly lax colleges of
Average $6,100 spent on each student 1992-1993
Teachers make average $34,027 (median of 1990 was $34,400)
Is anything proven about the quality of teacher training?
What kind of average is $6,100?
A median is not a great way to compare salaries and why
was 1990 used instead of 1992-93?
What further information do you need
before you can judge the impact of the
Our new police chief John Neu is not doing his job. The fact
is that Torrance is becoming a more dangerous place to
live. According to the latest statistics, the number of
crimes went from 1,471 to 1,537. That’s a 4.5% increase.
During the same time period, other South Bay cities
became safer. Manhattan Beach had 47 less crimes than
the year before and Hawthorne had 86 fewer crimes.
This argument that the Torrance police chief isn’t
doing his job is based on statistics about the crime
rate. You might want to know:
1. What was the pattern for crime in previous years
in Torrance? Maybe the current year was unusual
for some reason.
2. How many total crimes were there in Manhattan
Beach and Hawthorne?
3. How did other local cities compare?
4. What kind of crimes increased? Was it homicide,
rape, assault or auto theft?
1. Torrance had extremely low crime numbers in
2004 and 2005.
2. Manhattan Beach went from 356 in 2005 to 309 in
2006 (-13%). Hawthorne went from 2,406 to 2,320
3. Crime in Rancho Palos Verdes increased by 13%.
Rolling Hills increased by 75%. Lawndale
decreased by 2.7%. Lomita was unchanged.
4. There was a spike in the number of aggravated
assaults in Torrance in 2006. Burglary and auto
theft rose a little. Rape and robbery decreased.
Source: Altman, Larry. “South Bay Crime Report.” Daily Breeze. Sun. 11
March 2007. Page A1.
As Compared to….?
Another form of missing information is the lack of relevant
Americans belief in the value of international education
was not shaken after the Sept. 11 terrorist attacks. A recent
poll (March 2002) showed that 77% of the public supported
international course requirements in college.
More information about the poll at:
The Relevant Comparison
How does 77% support compare to previous years? It was
actually the same as the April 2000 survey.
Among other things, you might also be curious about:
Who was “the public” surveyed? Did they have college-age
How were the survey questions worded? Would so many
have been favorable if the students were going to the
middle east to study?
Who is ACE? Do they have a reason to push international
What’s Wrong with the Statistics?
Marriage drives men to drink and the problem seems to be
getting worse. Married men are twice as likely as bachelors
to become alcoholics, as evidenced by the fact that 66% of
all male alcoholics are married. In addition, the problem
has increased over the past 10 years, suggesting that
marriage is becoming increasingly stressful to the average
male. Statistics collected by the state of Michigan show
that there were over 15,000 married male alcoholics in
1998, compared with only 12,000 in 1988.
The Relevant Comparison
Concludes that marriage causes men to become alcoholic.
All you can really conclude is that more (two thirds) of
alcoholics are married.
How were people categorized as alcoholic? By asking
them straight out?
The statistics are misleading. Need to know:
The percentage of married men who are alcoholic versus the
percentage of single men who are.
The percentage of men who were alcoholics in 1998 vs. 1988. There
could be more men.
End of lecture