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Transcript of samplingmethods-120827123446-phpapp02
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By
Vijay Mehta
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What exactly IS a sample?
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What do qualitative researchers
worry about?
I want to see
the world
through theeyes of my
respondents.
I want to
describe the
context in a lotof detail.
I want to show
how social
change occurs.
Im interested inhow things
come to be.
I really want
my research
approach to be
flexible and
able to change.
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Social actors are notpredictable like objects.
Randomized events areirrelevant to social life.
Probability sampling is
expensive and inefficient.
Non-probability sampling is the
best approach.
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Types of samples
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Simple Random Sample
Get a list or sampling frame
a. This is the hard part! It must not systematically exclude
anyone.
Generate random numbers
Select one person per random numbers
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Systematic Random Sample
Select a random number, which will be known as
k
Get a list of people, or observe a flow of people(e.g., pedestrians on a corner)
Select every kthperson
Careful that there is no systematic rhythm to the flow orlist of people.
If every 4thperson on the list is, say, rich or senior or
some other consistent pattern, avoid this method
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Stratified Random
Sample
1. Separate your population into groups or
strata
2. Do either a simple random sample or
systematic random sample from there
a. Note you must know easily what the
strata are before attempting thisb. If your sampling frame is sorted by, say,
school district, then youre able to use this
method
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Multi-stage Cluster Sample
Get a list of clusters, e.g., branches of a
company
Randomly sample clusters from that list
Have a list of, say, 10 branches
Randomly sample people within those branches This method is complex and expensive
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The Convenience Sample
Find some people that are easy to find
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The Snowball Sample
Find a few people that are relevant to your topic.
Ask them to refer you to more of them.
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The Quota Sample
Determine what the population looks like in terms of
specific qualities.
Create quotas based on those qualities.
Select people for each quota.
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The Theoretical Sample
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Accidental sampling
A type of nonprobability sampling which involves
the sample being drawn from that part of the
population which is close to hand
The researcher using such a sample cannot
scientifically make generalizations about the total
population
In social science research, snowball sampling is a
similar technique
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Panel sampling
The method of first selecting a group of
participants through a random sampling
Period of data collection is called a "wave
Panel sampling can also be used to inform
researchers about within-person health changes
due to age
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How many?
Qualitative researchers seek saturation
How many isnt the issue. Do you understand the
phenomenon? Have you learned enough?
Mere numbers are irrelevant. You want verstehn or deep
understanding
Quantitative researchers seek statistical validity
Can you safely generalize to the population? Have yousystematically excluded anyone? (See the famous
sampling mistake)
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Improving Response Rates
Personalize the invitation
Offer money -- no strings attached
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Thank
You all