Preliminary Chapter

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Preliminary Chapter

• Statistics The science of learning from data
• Chapters 1-4 Tools and strategies for
  organizing, describing, analyzing data
• Chapter 5 How to produce data
• Chapter 6-9 Probability The study of chance
  behavior
• Chapter 10-15 Testing Claims/Computing estimates

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Ask the following questions

• Individuals People
• Variables Age, Gender, Job, Salary
• Every set of data comes with background
  information to help us understand the data!

• 1. What individuals do the data describe? How
  many individuals are there?
• 2. How many variables? Defs of these variables?
  What units? (lbs? kilos?)
• 3. Reasons the data was gathered? (For a sample
  or population)?

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Data Production

• Where can we find good data?
• ?Library
• ?Internet
• ?www.nces.ed.gov (Natnl Center for Education
  Statistics website)
• ?www.fedstats.gov (good source for projects)
• ? Statistical offices of foreign countries
  (www.statcan.ca, www.inegi.gob.mx )

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Is this good data?

• Suppose you want to find out if your classmates
  prefer cheeseburgers from McDonald's or Burger
  King. You decide to ask 50 people under the age
  of 20 which fast-food they prefer. In order to
  save time and energy, you conduct your survey at
  the McDonalds closest to campus. Is there a
  problem with this?

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Good and bad survey results

• In 1976, Shere Hite published The Hite Report on
  Female Sexuality, Seven Stories Press, Ny, Ny
  2004. The conclusions reported in her book were
  based on 3,000 returned surveys from 100,000
  surveys distributed by womens groups. The
  results were that women were highly critical of
  men. In what way might the authors findings have
  been biased?

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W-6, H

• W-6H Who What Why How Where When by Whom?
• Who is being studied
• What are the variables
• Why was the data gathered
• How was the data produced
• Where was the data gathered
• When was the data produced
• By Whom who directed it, can we trust it?

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State Region Pop SAT verbal SAT math taking No HS Teacherpay (1000)
CA PAC 35894 499 519 54 18.9 54.3
CO MTN 4601 551 553 27 11.3 40.7
CT NE 3504 512 514 84 12.5 53.6
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More Defs!

• Distribution of a Variable what values the
  variable takes on and how often it takes these
  values.
• The pattern of a variable is its distribution.

• Exploratory Data Analysis Examining data in
  order to describe their main features. (What do u
  see?)
• 2 steps
• 1) Examine the variables
• 2) Graph them.

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Do you wear your seat belt?
Region Wearing belts 2003 Wearing belts 1998
NE 74 66.4
MW 75 63.6
South 80 78.9
West 84 80.8
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Compare
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Dotplots

• Number of goals scored by the US womens soccer
  team in 34 games played in the 2004 season are
• 3 0 2 7 8 2 4 3 5 1 1 4 5 3 1 1 3 3 3 2 1 2 2 2 4
  3 5 6 1 5 5 1 1 5
• What does this tell us about the performance of
  the US womens team in 2004?

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TI-83 1 Var Stats L1
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Exploring Relationships between variables

• Air travelers would like their flights to arrive
  on time. Airlines collect data about on-time
  arrivals and report them to the department of
  Transportation. Heres one months data for
  flights from several western cities for two
  airlines

On time Delayed
Alaska Air 3274 501
American West 6438 787