1. Sampling Basics, Nonprobability and Simple Random Samples
Chapter 15

2. Six-Step Procedure for Drawing a Sample
Define the Target Population
Step 1
Identify the Sampling Frame
Step 2
Select a Sampling Procedure
Step 3
Determine the Sample Size
Step 4
Select the Sample Elements
Step 5
Collect the Data from the
Designated Elements
Step 6
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3. Target Population
The collection of elements about which the researcher wishes to make an inference or the totality of cases that conform to some designated specifications
Some possibilities:
Adults
Children
Households
Manufacturing firms
Wholesalers
Retailers
Nonprofit institutions
Credit card transactions
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4. The list of sampling units from which the sample will be drawn
Sampling Frame
The list of sampling units from which the sample will be drawn
Some Possibilities:
Individuals
Geographic Areas
Institutions
Credit card transactions
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5. Classification of Sampling Techniques
Sampling Designs
Nonprobability Samples
Convenience
Judgment
Quota
Probability Samples
Simple Random
Stratified
Proportionate
Disproportionate
Cluster
Systematic
Area
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6. Probability Sample
A sample in which each target population element has a KNOWN, NONZERO chance of being included in the sample
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7. Nonprobability Sample
A sample that relies on personal judgment somewhere in the selection process and therefore prohibits estimating the probability that any population element will be included in the sample.
Basic Types:
Convenience sample
A sample that is sometimes called an accidental sample because those included in the sample enter by accident in that they just happen to be where the study is being conducted when it is being conducted.
Judgment sample
A sample that is sometimes called a purposive sample in that the sample elements are handpicked because they are expected to serve the research purpose.
Quota Sample
A sample chosen in such a way that the proportion of sample elements possessing certain characteristics is approximately the same as the proportion of the elements with the characteristics in the population; each field worker is assigned a quota that specifies the characteristics of the people he or she is to contact.
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8. Parent Population of Discs in an UrnB C D E F
A=3
B=6
C=9
D=12
E=15
F=18
where
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9. Derived Population of all Possible Distinguished Samples
Mean Xj 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
ABC
ABD
ABE
ABF
ACD
ACE
ACF
ADE
ADF
AEF
BCD
BCE
BCF
BDE
BDF
BEF
CDE
CDF
CEF
DEF 18 21 24 27 30 33 36 39 42 45 6 7 8 9 10 11 12 13 14 15
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10. Relationship Between Parameters of Parent Population and Derived Population
Element
Total A B C D E F 3 6 9 12 15 18
 Xi N
Mean:  = = =
10.5 6 =
Variance: 2
 (Xi-) (3-10.5) ( )2 N = = 6
= = 6
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11. Relationship Between Parameters of Parent Population and Derived Population
 xj
j =1
Mean:
E( x )  = = = =
10.5 20 20 L
 ( xj
j =1
- E(x))2
Variance: σ2 _ x =
=( )2 + (7-10.5) ( )2 20
= 5.25
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12. Distribution of Variables in Parent and Derived Population
Parent Population 1
Absolute
Frequency
Values of X
Derived Population 3 2
Absolute
Frequency 1
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Values of x

13. Distribution of Sample Means for Samples of Various Sizes and Different Population Distributions
Parent Population - Distribution of X
Derived Population - Sampling Distribution of X
n=2
n=5
n=30
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14. Abridged List of Random Numbers
SLIDE 15-13