1. Chapter Ten
Basic
Sampling
Issues
Chapter Ten

2. Chapter Ten Objectives
Understand the concept of sampling
Learn the steps in developing a sampling plan
Understand the differences between probability and non-probability sampling methods
Understand the concepts of sampling error and non-sampling error
Become familiar with the different probability and non-probability samples
Understand the advantages of surveying over the Internet
Chapter Ten

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
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4. Developing a Sampling Plan
Chapter Ten

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
Chapter Ten

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
2. Non-probability sampling:
Specific elements from the population have been selected in a non-random manner
Chapter Ten

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
Chapter Ten

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
Non-Sampling Error:
Chapter Ten

9. Sampling and Non-Sampling Errors
Chapter Ten

10. Sampling Methods
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11. Probability Sampling Simple Random 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
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12. Probability Sampling Stratified 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.
Chapter Ten

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.
Chapter Ten

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
Chapter Ten

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
Chapter Ten