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

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