Quota sampling
Quota sampling method is a non-probability sampling and it can be defined as a sampling method of gathering representative data from a group. Application of quota sampling ensures that sample group represents certain characteristics of the population chosen by the researcher.
Quota sampling can be divided into two groups: controlled and uncontrolled.
Controlled quota sampling involves introduction of certain restrictions in order to limit researcher’s choice of samples.
Uncontrolled quota sampling, on the other hand, resembles convenience sampling method in a way that researcher is free to choose sample group members according to his/her will.
The main difference between quota and stratified sampling can be explained in a way that in quota sampling researchers use non-random sampling methods to gather data from one stratum until the required quota fixed by the researcher is fulfilled. Accordingly, the quota is based on the proportion of subclasses in the population.
Application of Quota Sampling: an Example
Let’s assume your research objective is to evaluate the impact of cross-cultural differences on employee motivation in Virgin Media in the UK. You need to assess the effectiveness of employee motivational tools taking into account gender differences among the workforce.
Quota sampling can be applied in the following manner:
1. Dividing the population into specific groups. Virgin Media employees in the UK as the sampling frame need to be divided into the following five groups according to their cultural background:
- European
- Asian (India)
- Asian (China)
- Black (African)
- Other
2. Calculating a quota for each group. You supervisor confirms that in order to achieve research objectives, 30 representatives from each group and the total sample size of 150 respondents would be appropriate.
3. Determining specific condition(s) to be met and quota in each group
Both genders, males and females need to be represented equally in your sample group. This is an important condition that has to be satisfied. Accordingly, you recruit 15 males and 15 females from each group.
Application of quota sampling ensures that sample group represents certain characteristics of the population chosen by the researcher. In example above, an equal representation of both genders, males and females has been chosen as an important characteristic of sampling.
Advantages of Quota Sampling
1. Quota sampling emerges as an attractive choice when you are pressed for time, because primary data collection can be done in shorter time.
2. The application of quota sampling can be cost-effective.
3. Quota sampling is not dependent on the presence of the sampling frames. In occasions where suitable sampling frame is absent, quota sampling may be the only appropriate choice available.
Disadvantages of Quota Sampling
1. Same as other non-probability samplingmethods, in quota sampling it is not possible to calculate the sampling error and the projection of the research findings to the total population is risky.
2. While this sampling technique might be very representative of the quota-defining characteristics, other important characteristics may be disproportionately represented in the final sample group.
3. There is a great potential for researcher bias and the quality of work may suffer due to researcher incompetency and/or lack of experience
My e-book, The Ultimate Guide to Writing a Dissertation in Business Studies: a step by step approach contains a detailed, yet simple explanation of sampling methods. The e-book explains all stages of the research process starting from the selection of the research area to writing personal reflection. Important elements of dissertations such as research philosophy, research approach, research design, methods of data collection and data analysis are explained in this e-book in simple words. John Dudovskiy
[1] Saunders, M., Lewis, P. & Thornhill, A. (2012) “Research Methods for Business Students” 6th edition, Pearson Education Limited