# Bill of Materials for Construction Samples

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"Bill of Materials for Construction Samples"

```					Sampling and Questionnaires

Bill Reimer
October 31, 2005
reimer@vax2.concordia.ca
http://reimer.concordia.ca/teaching

11/22/2010             Bill Reimer          1
Outline
 Sampling
 Questionnaire construction

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Sampling Objective
    Get a lot of information with little cost

Sample
Population

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Sample sizes for a population of 10,000

4500                                                       4147
4000
3500
Sample Size

3000
2401
2500                                                              95% Confidence
2000                                                              99% Confidence
1500                                             1037
1000                                         600
461
500         96 166      150259   267

0
10%         8%       6%          4%          2%
Range of acceptable error
(Accuracy)
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3 Rules of Scientific Sampling

 each unit in the population has an equal
chance of being chosen
 we must know the chance of each
member being chosen
 each selection must be independent
from the others

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To what do you want to
generalize?

 People
 Households
 Trees
 Leaves
These are the Units of Analysis

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To which units do you want to
generalize?

 Women in Québec?
 Citizens of Montréal?
 Trees in boreal forests?
This is the Population

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The Population

 Is the collection of units to which you
want to generalize
 It may be abstract
 It may be concrete
But it must be clear

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From what will you choose your
sample?

A          list of units?
A          region or place?
A          drawer or computer file?
A          particular time?

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The Sample Frame may not
match the Population

Population

Sample Frame

…but try to get them close
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Sampling Requirements:

 Identify the population
 Is the sample frame reasonable?
 Does it meet the 3 conditions of scientific
sampling?

We can seldom meet all 3 conditions!

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Types of Samples

   Probability
 Generalizability
 Efficient

   Non-probability
 Exploratory
 Strategic

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Simple Random Sampling

                   
                   
 Equal chance of being
                            chosen
                   
                           We know the chance
 Each selection
                   
                   
                            independent

From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

11/22/2010                            Bill Reimer                               13
Systematic Sampling
Random selection                  Determine sample rate
                            (8/40)
 Random selection of 1st
                    
                    
                            case
                    
                           Every nth case (n=5)
 Watch for regularities in
                    
                    
the sample frame
From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

11/22/2010                            Bill Reimer                               14
Stratified Random Sampling
                            Separate sample frame
                             into strata
                   
                            Take random (or










systematic) sample
                             from each strata
 May be proportionate
                   

or disproportionate
From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

11/22/2010                            Bill Reimer                               15
Cluster Sampling
 Divide population into
                           clusters
                   
                          Randomly select clusters
                          Collect data on all cases











in cluster
 Watch cluster
composition
From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

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Cluster Sampling - Montréal

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Non-Probability Samples
 Accidental
 Purposive

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Convenience Sample

                   
                   
 Choose most
                            convenient people
                   
                           Subject to multiple
                   
biases
                   
                   

From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

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Volunteer Sampling

                            Directly
                    

 Selected groups

                    Unclear biases

From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

11/22/2010                             Bill Reimer                              20
Strategic Sampling




 Handpick respondents
                     for strategic purposes

 Useful for marginalized


or small groups
                                Control biases by
specifying criteria
From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

11/22/2010                            Bill Reimer                               21
Snowball Sampling

             
 Identify strategic
respondent
                         
 Continue the process
 Use multiple starts to
                          
avoid network biases
From: O’Leary, Z (2004) The Essential Guide to Doing Research, London: Sage, Ch 8.

11/22/2010                             Bill Reimer                              22
Probability Samples – Multiple
    Mixture of various techniques

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Sample Size Depends On

 Size of the population
 Accuracy desired
 Confidence desired
 Variation in the phenomenon investigated

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Assignment
    Specify a research question you would like to
    Describe a sampling procedure along with the
data you would collect to answer the question.
    Identify the following:
    the   population
    the   sample unit
    the   sample frame
    the   type of sample

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Samples
   Non-probability
   Accidental
   Purposive
   Probability
   Simple random
   Systematic
   Stratified:
• Proportionate
• Disproportionate
   Cluster
   Multiple
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Constructing Questionnaires

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Types of Research Interviews
    Questionnaires
    Closed and some open-ended questions
    Semi-structured interviews
    Open and some closed-ended questions
    Unstructured interviews
    Open-ended questions

Research Interviews are NOT what you see on TV

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Questionnaires                     Semi-structured
    Economic                           High response rates
    Speedy                             Can ask complicated
    Minimal interviewer                 questions
bias                               Can follow-up Qs
    Anonymity                          Can observe
    Low response rates                 Expensive
    Limited exploration                Time consuming
    Comparison easy                    Comparison difficult
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Preparing Questions
specific questions
 Clarify the RESEARCH question
 Identify the types of information required
 Within each of the types of information
brainstorm for specific questions to ask
 Rearrange questions

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Question Order
 Leave sensitive issues for later - once
rapport has been established
 Follow from general to specific
 Use tables and grids where appropriate
 Use cards for sensitive issues if
appropriate
 Prepare your probes if interview
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Anticipate the Analysis

 Produce dummy tables
 Work backwards from your analysis

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Format examples
 Contingency question
 Full filter question
 Quasi-filter question
 Closed question
 Partially open question
 Open question
 Probes

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Simple, Mutually Exclusive
    What is your gender? (Circle the
appropriate number)
 Female . . . . . . . . . . . . . . . 1     5

 Male . . . . . . . . . . . . . . . . . 2

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Multiple Choice, not Mutally
Exclusive
    What modes of transportation did you
used to get to school last week? (Circle all
that apply)
• Metro . . . . . . . . . . . . . . . . .     1    6

• Bus . . . . . . . . . . . . . . . . . . .   1    7

• Car . . . . . . . . . . . . . . . . . . .   1    8

• Bicycle . . . . . . . . . . . . . . . . .   1    9

• Walk . . . . . . . . . . . . . . . . . .    1    10

_____________________                  1   |__|__| 11-12

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Rank-order
   Rank order the 3 most important aspects of
your job (Place 1 beside the most important, 2
beside the next most important, and 3 beside
the next most important)
• Money . . . . . . . . . . . . . . . . . . |___|     13

• Security . . . . . . . . . . . . . . . . . |___|    14

• New experiences . . . . . . . . . . |___|           15

• Power . . . . . . . . . . . . . . . . . . |___|     16

• Excitement . . . . . . . . . . . . . . |___|        17

________________________ |___|                    |__|__| 18-19
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Pretest, pretest, pretest
 Use your friends and family
 Discuss
 Where it was clear or not clear
 What they thought about when responding
to each question
 What they thought you were getting at

 Move to colleagues
 Check it out on people who are similar to
those you will eventually survey
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Problem Questions
   Jargon, slang, abbreviations
   What is your Internet browser?
   Ambiguity, confusion, vagueness
   Emotional language and prestige bias
   Should we put murderous terrorists in jail?
   Do you support Prime Minister Chretien’s policy on
   Double-barrelled questions
   Should marijuana be legalized for medical or other
purposes?
Problem Questions – con’t
    Do you feel that governments should have
less power to interfere in business?
    Beyond respondent’s competence
    Does your mother support extramarital sex?
    False premises
    How can we halt the rising crime rate?

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Problem Questions – con’t
    Future intentions
    How will you vote in the next federal
election?
    Overlapping or unbalanced response
categories
    What is your opinion regarding abortion?
• Very favourable
• Favourable
• Neutral
11/22/2010   • Opposed           Bill Reimer       40
Questionnaire Construction
 The amount of time spent in the
preparation of the questionnaire is
directly related to the value of the results.
 Surveys usually cost a lot and you can't
redo them.
 Know what you are wanting to discover

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Research Strategies
 Questionnaires for generalizability
 Exploration: well selected, in-depth
interviews
 Use interviews to design survey
 Use comparisons

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Sampling and Questionnaires

Bill Reimer
October 31, 2005
reimer@vax2.concordia.ca
http://reimer.concordia.ca/teaching

11/22/2010             Bill Reimer          44

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