Quota sampling involves dividing a population into subgroups and selecting samples to represent each subgroup in proportion to its share of the overall population. It allows investigation of traits in subgroups and relationships between subgroups. While quick and cost-effective, it cannot calculate sampling error and may not represent the entire population. Snowball sampling relies on referrals from initial subjects to identify new subjects. It is useful for hidden populations but represents less control and potential sampling bias. Both methods limit statistical inference and introduce subjectivity.

1. Quota Sampling

2. Types of quota sampling
Controlled quota sampling
– involves
introduction of
certain restrictions
in order to limit
researcher’s choice
of samples.
Uncontrolled quota
sampling
– resembles convenience
sampling method in a
way that researcher is
free to choose sample
group members
according to his/her
will.

3. How to use quota sampling?
1. Divide the sample population into
subgroups
2. Figure out the weightages of subgroups
3. Select an appropriate sample size
4. Survey while adhering to the subgroup
population proportions

4. When to use quota sampling?
– To investigate a trait or characteristic of
a certain subgroup
– To observe relationships between
subgroups

5. Advantages
– Time constraint (comparing to stratified)
– Cost-effective
– Absence of sampling frame

6. Disadvantages
– Unable to calculate sampling error
– Sampling bias
– Quality of the work may suffer
– Does not represent the entire population
– Cannot make statistical inferences

7. Snowball sampling

8. Types of snowball sampling

9. Advantages
– Facilitates to access hidden populations
– Can produce in-depth results and relatively
quickly
– Cost-effective
– Simple process
– Less planning
– Fewer workforce

10. Disadvantages
– Little control over the sampling method
– Representativeness if not guaranteed
– Sampling bias
– Unable to determine sampling error
– Takes time
– Cannot make statistical inferences
– Some degree of subjectivity

11. Quota sampling vs Snowball
sampling
Quota sampling Snowball sampling
Characteristics Common (Eg: gender, age) Very rare
Relies on Researchers judgment or
convenience
First respondent
Time Low Varies depending on trust