Sampling techniques: Advantages and disadvantages



Sampling techniques: Advantages and disadvantages

|Technique |Descriptions |Advantages |Disadvantages |

|Simple random |Random sample from whole population|Highly representative if all subjects |Not possible without complete list of |

| | |participate; the ideal |population members; potentially uneconomical|

| | | |to achieve; can be disruptive to isolate |

| | | |members from a group; time-scale may be too |

| | | |long, data/sample could change |

|Stratified random |Random sample from identifiable |Can ensure that specific groups are |More complex, requires greater effort than |

| |groups (strata), subgroups, etc. |represented, even proportionally, in the|simple random; strata must be carefully |

| | |sample(s) (e.g., by gender), by |defined |

| | |selecting individuals from strata list | |

|Cluster |Random samples of successive |Possible to select randomly when no |Clusters in a level must be equivalent and |

| |clusters of subjects (e.g., by |single list of population members |some natural ones are not for essential |

| |institution) until small groups are|exists, but local lists do; data |characteristics (e.g., geographic: numbers |

| |chosen as units |collected on groups may avoid |equal, but unemployment rates differ) |

| | |introduction of confounding by isolating| |

| | |members | |

|Stage |Combination of cluster (randomly |Can make up probability sample by random|Complex, combines limitations of cluster and|

| |selecting clusters) and random or |at stages and within groups; possible to|stratified random sampling |

| |stratified random sampling of |select random sample when population | |

| |individuals |lists are very localized | |

|Purposive |Hand-pick subjects on the basis of |Ensures balance of group sizes when |Samples are not easily defensible as being |

| |specific characteristics |multiple groups are to be selected |representative of populations due to |

| | | |potential subjectivity of researcher |

|Quota |Select individuals as they come to |Ensures selection of adequate numbers of|Not possible to prove that the sample is |

| |fill a quota by characteristics |subjects with appropriate |representative of designated population |

| |proportional to populations |characteristics | |

|Snowball |Subjects with desired traits or |Possible to include members of groups |No way of knowing whether the sample is |

| |characteristics give names of |where no lists or identifiable clusters |representative of the population |

| |further appropriate subjects |even exist (e.g., drug abusers, | |

| | |criminals) | |

|Volunteer, |Either asking for volunteers, or |Inexpensive way of ensuring sufficient |Can be highly unrepresentative |

|accidental, |the consequence of not all those |numbers of a study | |

|convenience |selected finally participating, or | | |

| |a set of subjects who just happen | | |

| |to be available | | |

Source: Black, T. R. (1999). Doing quantitative research in the social sciences: An integrated approach to research design, measurement, and statistics. Thousand Oaks, CA: SAGE Publications, Inc. (p. 118)

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