Sampling

FdA and BA (Hons) Counselling with Brief Interventions

Counselling Research

Aims

By the end of this session you will be able to:

• Explain what sampling means• Identify the difference between probability

and non-probability sampling• Identify a sampling method appropriate for

your project

Why?

Here’s Why …

A credible and appropriate sampling strategy will strengthen your research methodology

Communicating a critical awareness of sampling when writing your project or dissertation will add gravitas to your work.

What is Sampling?

It’s too expensive to conduct research on a large population …

So we conduct research on a sample of that population …

How we choose our sample can be important, depending on the type of research we are undertaking …

Sampling in Quantitative Research

• I want to generalise my findings

• I want the research to be repeatable

• I want to remove subjectivity and bias

• It’s important that the sample is representative

Sampling in Qualitative Research

• I want to focus on individual stories and subjective experience

• I am interested in context and themes

• I am interested in ‘saturation’

Types of Sampling

In probability sampling we know what the likelihood is of each subject being chosen

Types of Sampling

Non- Probability

Sample

Convenience Snowball Quota

Probability Sampling #1

Random Sample1. Get a list (the sampling frame)2. Generate random numbers3. Select one person per random number

Probability Sampling #2

Systematic Random Sample1. Select a number e.g. 52. Get a list (the sampling frame)3. Select every e.g. 5th person on the list

Probability Sampling #3

Stratified Random Sample1. Your population is separated into groups2. Do a random or a systematic random sample

for each of those groups

Non-probability Sampling #1

The Convenience SampleChoose participants that are handy

Purposive sampling The researcher chooses participants based on whether he or she thinks they will be appropriate for the study

Non-probability Sampling #2

The Snowball SampleAsk participants to refer you to more participants

Non-probability Sampling #3

Quota Sampling1. Determine what the population is like

according to specific qualities2. Determine quotas for each quality3. Select people to fulfil each quota

Sampling and Your Research

Consider the sampling method you are going to use:

1. What would be appropriate?2. What would add credibility to your research?3. What fits with your methodology?4. What is do-able?

Conclusions

1. Consider how you are choosing your participants

2. Write about your sampling strategy in your methodology

3. Provide a rationale for your approach4. Demonstrate an understanding of sampling

and how it applies to your research