Do Now

1
Do Now

• Figure out how tall you are in inches (e.g. 57
  67) and write in on the whiteboard next to
  your name
• If you dont have L1, then do STAT ? SetUpEditor
• If you need to clear the list, go to the very top
  and press CLEAR then ENTER.
• Enter our heights into L1.
• See p.11 for reference.

2
Objectives

• Chapter 2 Data
• What are data?
• What is a good way to organize data?
• How do we enter data into the calculator?
• What about the datas context do we care about?
  (The Ws)
• Example critical reading

3
Data Collection

• Obtain everyones height
• Clear L1 by going to the top and pressing CLEAR
  ENTER
• Enter our height data into calc
• Find the average by looking at the first line of
  output after pressing STAT ? CALC ? 1 and ENTER.

4
Data Collection

• If there were more things we were recording, what
  would be a good way to organize the data?

5
What Are Data?

• Data can be numbers, record names, or other
  labels.
• Not all data represented by numbers are numerical
  data (e.g., 1male, 2female).
• Data are useless without their context (what
  does 233, 241, 198, 303 mean?)

6
The Ws

• To provide context we need the Ws
• Who
• What (and in what units)
• When
• Where
• Why (if possible)
• and How
• of the data.
• Lets use the WashPost article as an example

7
Who

• The Who of the data tells us the individual cases
  or observations for which (or whom) we have
  collected data.
• Individuals who answer a survey are called
  respondents.
• People on whom we experiment are called subjects
  or participants.
• Animals, plants, and inanimate subjects are
  called experimental units.

8
Who (cont.)

• The sample size is an important part of the Who
• Although this is not the books definition, we
  also want to know Who did the study (and in
  what journal/magazine was it written)

9
What

• What about the Who are we recording?
• Variables are characteristics recorded about each
  individual (e.g. height, weight, age, gender).

10
What

• A categorical (or qualitative) variable names
  categories and answers questions about how cases
  fall into those categories.
• Categorical examples sex, race, ethnicity
• A quantitative variable is a measured variable
  (with units) that answers questions about the
  quantity of what is being measured.
• Quantitative examples income (), height
  (inches), weight (pounds)

11
What

• Example In a student evaluation of instruction
  at a large university, one question asks students
  to evaluate the statement The instructor was
  generally interested in teaching on the
  following scale
• 1 Disagree Strongly
• 2 Disagree
• 3 Neutral
• 4 Agree
• 5 Agree Strongly

12
What

• Question Is interest in teaching categorical or
  quantitative?
• Variables like interest in teaching are often
  called ordinal variables.
• With an ordinal variable, look at the Why of the
  study to decide whether to treat it as
  categorical or quantitative.

13
Identifying Identifiers

• Identifier variables are categorical variables
  with exactly one individual in each category.
• Examples Social Security Number, ISBN, FedEx
  Tracking Number
• Dont be tempted to analyze identifier variables.

14
Where, When

• When and Where give us some nice information
  about the context.
• Example Values recorded at a large public
  university may mean something different than
  similar values recorded at a small private
  college.
• A study done in 1910 might no longer be valid in
  light of recent evidence

15
Why

• Why was the study done?
• What are the explicit motives?
• Can you think of any ulterior motives?

16
How

• How was the study done?
• How were the subjects selected?
• Are there any possible sources of bias?
• Details of exactly what to look for will be
  discussed in Ch. 11 12.

17
What Can Go Wrong?

• Just because your variables values are numbers,
  dont assume that its quantitative.
• Always be skepticaldont take data for granted.
  Keep digging until you find the truth.
  Statistics is like detective work.

18
What Can Go Wrong?

• The Who refers to the target of the study, not
  the person who does the study (although this is
  also useful information)
• A date in an article does not necessarily tell
  you the When.
• If something is not given, write not given. DO
  NOT ASSUME. DO NOT JUMP TO CONCLUSIONS. The
  brain likes to do these things.

19
Analyzing writing involving statistics

• Washington Post article

20
Homework

• Complete questionnaire on website
• Now that you know what we are looking for with
  regards to the Ws, revise your responses
  underneath your original ones. Remember to write
  in complete sentences.
• Quiz on Tuesday
• Quizzes are cumulative, but focus on the material
  since the last assessment
• This makes it more difficult, but will make you a
  better test taker come May.