Sampling Methods Explained

Study Notes

To obtain a sample of 150 from a list of 1,500 students, select a set of numbers like 1 to 15, and then take every 15th name on the list until the total number of respondents is achieved.

Population divides into different strata (groups).
Sampling follows this division.
Criteria such as age, gender, and educational qualifications can separate a population into strata.
In a study on the effects of smoking on high school students, researchers may select equal numbers of students from freshman, sophomore, junior, and senior levels.

Used in large-scale studies.
Clusters represent samples of the entire population.
Establish clusters, draw a simple random sample of the clusters, and sample the members of the chosen clusters.
Sampling can be difficult and time-consuming.
In a study to interview 100 teachers across the country could use cluster sampling.
Researchers may select regions (first cluster).
Researchers may select schools (second cluster).
Can then select the number of teachers.

Disregards random selection of subjects.
Subjects chosen based on availability, the study's purpose, or the researcher's discretion.
This is not a scientific method and is common in qualitative research.

Respondents are chosen based on the convenience for the researcher.
Also known as accidental or incidental sampling.
To study elementary students in a school while dealing with the study's constraints, researchers may choose elementary pupils present during their visit as respondents.

Involves handpicking subjects to suit specific intentions, also termed judgmental sampling.
In a study on honor students, honor students are chosen and the necessary number of respondents needed, excluding all other students.

Similar to stratified sampling.
Population divides into strata, and specific proportions are deliberately set in the sample, regardless of whether the resulting proportion reflects the total population.
Helps ensure the inclusion of a particular segment of the population.
When surveying employees on company policies, researchers might set a quota of respondents from a small department to ensure adequate representation.

Involves people who self-select into the survey, often having a strong interest in the survey's main topic.
An online poll on a show is a volunteer sample, as the viewers choose the sample, not the survey administrator.

Does not give a specific set of samples.
For studies involving unspecified groups like street children, drug dependents, gang members, informal settlers, and street vendors.
Achieved by asking a participant to suggest someone else suitable for the study.