1. Chapter Eleven: Basic Sampling Issues

2. Chapter Eleven: Basic Sampling Issues
Understand the concept of sampling
Describe the steps in developing a sampling plan
Differentiate between probability and non-probability sampling methods
Explain the concepts of sampling error and non-sampling error
Describe the different probability and non-probability samples
Understand the advantages of surveying over the Internet

3. The Concept of Sampling
Population
Sample
Census
Why samples are acceptable in research:
Sampling is considered statistically sound
A census is expensive and time-consuming
It may be impossible to find an accurate, up-to-date sample frame for a full census
Fewer opportunities for errors / biases to impact data

4. Developing a Sampling Plan

5. Developing a Sampling Plan
Step One: Define the Population of Interest
Target audience
Demographics, geographics, behavioural characteristics, awareness, etc.
Used for screening respondents for “fit” to complete survey
Step Two: Choose a Data-Collection Method
Survey method: mail, Internet, telephone, mall-intercept, etc.
Step Three: Identify a Sampling Frame
A list of the selected population
People from the list will become sample units

6. Developing a Sampling Plan
Step Four: Select a Sampling Method
Probability sampling:
Every element of the population has a known likelihood of selection for the survey
Non-probability sampling:
Specific elements from the population have been selected in a non-random manner

7. Developing a Sampling Plan
Step Five: Determine the Sample Size
Based on factors such as:
Level of accuracy you want to achieve
Time and money you have to complete survey study
Sampling collection method
Step Six: Develop Operational Procedures
Plan to conduct probability or non-probability sampling
Determine the phases of the sample selection process
Multi-stage sampling involves combining sampling methods
Step Seven: Execute the Sampling Plan
The execution phase of the research
Administering the questionnaire

8. Sampling and Non-Sampling Errors
An error that occurs because the sample selected is not perfectly representative of the population
All error other than sampling error; also called measurement error

9. Sampling and Non-Sampling Errors

10. Sampling Methods

11. Probability Sampling Simple Random Sampling: Systematic Sampling:
Assign a number to every element of the population and randomly select elements
Systematic Sampling:
A sample in which the entire population is numbered and elements are selected using a skip interval
Every nth name is selected
Skip Interval = Population Size
Sample Size

12. Probability Sampling Stratified Sampling: Cluster Sampling:
A more representative approach, through simple random sampling of two or more mutually exclusive and exhaustive subsets
Cluster Sampling:
Sampling units are selected from a number of small geographic areas to reduce data-collection costs
Examples: cities, city blocks, etc.

13. Non-Probability Sampling
Convenience:
A sample based on using people who are easily accessible, such as mall intercepts or other high-traffic locations
“Person on the street”
Judgement:
Selection criteria based on researcher’s personal judgment about representativeness of the population under study
The researcher selects who should be in the study based on observed cues such as gender, age, usage of product, etc.

14. Non-Probability Sampling
Snowball:
Respondents are selected based on referrals from initial respondents
Used when sample unit characteristics are quite rare or very difficult to find
Quota:
Quotas, based on demographic or classification factors selected by the researcher, are established for population subgroups

15. Internet Sampling Advantages: Disadvantages:
Respondents can complete survey at their convenience
Data collection is relatively inexpensive
Survey software can facilitate data-collection process
Survey can be completed quickly
Disadvantages:
Sample might not be representative
Cannot always ensure who completes survey
Maintaining respondent confidentially can be a challenge
Data security issues can be difficult to manage

16. Copyright
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