day2

Document Sample
day2 Powered By Docstoc
					                                                                                                  i

                          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
                                                                                                  1
                                                                                                  i
         • 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
                                                                                                  2
                                                                                                  i
         • 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
                                                                                                  3
                                                                                                  i
         • 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
                                                                                                  4
                 Frequency Distributions                                                          i




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  5
                         Percentiles/Deciles                                                      i




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  6
                                             Scales                                               i
         • 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
                                                                                                  7
                                 Nominal Scale                                                    i
         • 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
                                                                                                  8
                                  Ordinal Scale                                                   i
         • 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
                                                                                                  9
                                  Interval Scale                                                  i
         • 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
                                                                                                  10
                                      Ratio Scale                                                 i
         • 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
                                                                                                  11
                               Scales (cont’d.)                                                   i
         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
                                                                                                  12
                               Scales (cont’d.)                                                    i
         Nominal                   Ordinal                    Interval                   Ratio

         Name                      =                          =                          =

         Mutually-                 =                          =                          =
         exclusive
                                   Ordered                    =                          =

                                                              Equal                      =
                                                              interval
         Gender,                   Class rank,                Days of wk.,               Inches,
         Yes/No                    ratings                    temp.                      dollars
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                   13
                          Critical Skepticism                                                     i
         • 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
                                                                                                  14
                       Company is hurting.                                                        i
         • 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
                                                                                                  15
                                                Sale!                                             i
         • “Save 100%”

         • I doubt it.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  16
                                    Probabilities                                                 i
         • “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 Spanish-
                 American 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
                                                                                                  17
                 Are all results reported?                                                        i
         • “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
                                                                                                  18
                         Sampling problems                                                        i
         • “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
                                                                                                  19
                 Correlation ≠ Causation                                                          i
         • 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
                                                                                                  20
                                Remember . . .                                                    i
         •   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
                                                                                                  21
                                                   ???                                            i
         • 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
                                                                                                  22
          Quote on front of Huff book:                                                            i
         • “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
                                                                                                  23
                                             Claims                                               i
         • “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
                                                                                                  24
                                       Homework                                                   i
         • 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
                                                                                                  25

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:1
posted:11/4/2012
language:English
pages:25