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SAMPLINGMETHODS
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Sample vs. Population
Population
Sample
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What do qualitative
researchers worry about?
I want to seethe world
through theeyes of myrespondents.
I want todescribe the
context in alot of detail.
I want to showhow socialchangeoccurs. Iminterested inhow thingscome to be.
I really wantmy researchapproach to
be flexibleand able tochange.
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Social actors are notpredictable likeobjects.
Randomized events areirrelevant to social life.
Probability sampling is
expensive and inefficient.
Non-probability sampling isthe best approach.
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Types of samples
Sampling method
Probabilitic Non- Probabilitic
1. Simple Random Sample2. Systematic Random Sample3. Stratified Random Sample4. Cluster sample5. Multi Cluster Sample
Without Replacement
With Replacement1. Judgmental
sampling2. Quota
Sampling3. Snow ball
Sampling
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Simple Random Sample
Get a list or sampling frame
a. This is the hard part! It must not systematically excludeanyone.
Generate random numbers
Select one person per random numbers
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Systematic Random Sample
Select a random number, which will be knownas k
Get a list of people, or observe a flow of people(e.g., pedestrians on a corner)
Select every kth person
Careful that there is no systematic rhythm to theflow or list of people.
If every 4thperson on the list is, say, rich or senioror some other consistent pattern, avoid this method
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Stratified Random Sample
1. Separate your population into groups orstrata
2. Do either a simple random sample orsystematic random sample from there
a. Note you must know easily what the
strata are before attempting this
b. If your sampling frame is sorted by, say,school district, then youre able to usethis method
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Multi-stage Cluster Sample
Get a list of clusters, e.g., branches of acompany
Randomly sample clusters from that list
Have a list of, say, 10 branches
Randomly sample people within thosebranches
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 toyour topic.
Ask them to refer you to more of them.
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The Quota Sample
Determine what the population looks like in termsof 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 whichinvolves the sample being drawn from thatpart of the population which is close to hand
The researcher using such a sample cannotscientifically make generalizations about thetotal population
In social science research, snowballsampling is a similar technique
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Panel sampling
The method of first selecting a group ofparticipants through a random sampling
Period of data collection is called a"wave
Panel sampling can also be used toinform researchers about within-personhealth changes due to age
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How many?
Qualitative researchers seek saturation
How many isnt the issue. Do you understandthe phenomenon? Have you learned enough?
Mere numbers are irrelevant. You wantverstehn or deep understanding
Quantitative researchers seek statistical
validity Can you safely generalize to the population?
Have you systematically 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