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LIS 397.1
Introduction to Research in Library and
Information Science
Summer, 2003
Day 2 – Thoughtful Thursday
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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• There are three kinds of lies: lies,
damned lies, and statistics.
– Benjamin Disraeli (1804 – 1881), British
politician
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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• Statistics are like a bikini. What they
reveal is suggestive, but what they
conceal is vital.
– Aaron Levenstein, U.S. politician
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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• The statistics on sanity are that one out
of every four Americans is suffering from
some form of mental illness. Think of
your three best friends. If they're okay,
then it's you.
– Rita Mae Brown, U.S. author
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Frequency Distributions
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Percentiles/Deciles
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Scales
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• The data we collect can be represented
on one of FOUR types of scales:
– Nominal
– Ordinal
– Interval
– Ratio
• “Scale” in the sense that an individual
score is placed at some point along a
continuum.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Nominal Scale
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• Describe something by giving it a name.
(Name – Nominal. Get it?)
• Mutually exclusive categories.
• For example:
– Gender: 1 = Female, 2 = Male
– Marital status: 1 = single, 2 = married, 3 =
divorced, 4 = widowed
– Make of car: 1 = Ford, 2 = Chevy . . .
• The numbers are just names.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Ordinal Scale
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• An ordered set of objects.
• But no implication about the relative
SIZE of the steps.
• Example:
– The 50 states in order of population:
•
•
•
•
1 = California
2 = Texas
3 = New York
. . . 50 = Wyoming
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Interval Scale
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• Ordered, like an ordinal scale.
• Plus there are equal intervals between each
pair of scores.
• With Interval data, we can calculate means
(averages).
• However, the zero point is arbitrary.
• Examples:
– Temperature in Fahrenheit or Centigrade.
– IQ scores
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Ratio Scale
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• Interval scale, plus an absolute zero.
• Sample:
– Distance, weight, height, time (but not years
– e.g., the year 2002 isn’t “twice” 1001).
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Scales (cont’d.)
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It’s possible to measure the same attribute on
different scales. Say, for instance, your
midterm test. I could:
• Give you a “1” if you don’t finish, and a “2” if
you finish.
• “1” for highest grade in class, “2” for second
highest grade, . . . .
• “1” for first quarter of the class, “2” for second
quarter of the class,” . . .
• Raw test score (100, 99, . . . .).
– (NOTE: A score of 100 doesn’t mean the person
“knows” twice as much as a person who scores 50,
he/she just gets twice the score.)
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Scales (cont’d.)
Nominal
Ordinal
Interval
Ratio
Name
=
=
=
Mutuallyexclusive
=
=
=
Ordered
=
=
Equal
interval
=
Days of wk.,
temp.
Inches,
dollars
Gender,
Yes/No
Class rank,
ratings
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Critical Skepticism
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• Remember the Rabbit Pie example from
yesterday.
• The “critical consumer” of statistics
asked “what do you mean by ’50/50’”?
• Let’s look at some other situations and
claims.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Company is hurting.
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• We’d like to ask you to take a 50% cut in
pay.
• But if you do, we’ll give you a 60% raise
next month. OK?
• Problem: Base rate.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Sale!
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• “Save 100%”
• I doubt it.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Probabilities
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• “It’s safer to drive in the fog than in the
sunshine.” (Kinda like “Most accidents occur
within 25 miles of home.” Doesn’t mean it gets
safer once you get to San Marcos.)
• Navy literature around WWI:
– “The death rate in the Navy during the SpanishAmerican war was 9/1000. For civilians in NYC
during the same period it was 16/1000. So . . . Join
the Navy. It’s safer.”
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Are all results reported?
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• “In an independent study [ooh, magic
words], people who used Doakes
toothpaste had 23% fewer cavities.”
• How many studies showed MORE
cavities for Doakes users?
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Sampling problems
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• “Average salary of 1999 UT grads –
“$41,000.”
• How did they find this? I’ll bet it was
average salary of THOSE WHO
RESPONDED to a survey.
• Who’s inclined to respond?
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Correlation ≠ Causation
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• Around the turn of the century, there
were relatively MANY deaths of
tuberculosis in Arizona.
• What’s up with that?
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Remember . . .
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•
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I do NOT want you to become cynical.
Not all “media bias” is intentional.
Just be sensible, critical, skeptical.
As you “consume” statistics, ask some
questions . . .
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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???
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• Who says so? (A Zest commercial is unlikely to tell
you that Irish Spring is best.)
• How does he/she know? (That Zest is “the best
soap for you.”)
• What’s missing? (One year, 33% of female grad
students at Johns Hopkins married faculty.)
• Did somebody change the subject? (“Camrys
are bigger than Accords.” “Accords are bigger than
Camrys.”)
• Does it make sense? (“Study in NYC: Working
woman with family needed $40.13/week for adequate
support.”)
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Quote on front of Huff book:
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• “It ain’t so much the things we don’t
know that get us in trouble. It’s the
things we know that ain’t so.”
Artemus Ward, US author
• Being a critical consumer of statistics will
keep you from knowing things that ain’t
so.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Claims
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• “Better chance of being struck by
lightening than being bitten by a shark.”
• Tom Brokaw – Tranquilizers.
• What are some claims you all
heard/read?
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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Homework
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• LOTS or reading. See syllabus.
• Send a table/graph/chart that you’ve
read this past week. Send email by
noon, Monday, 6/9/2003.
See you Tuesday.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
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