Sampling techniques

  • Created by: Saf54
  • Created on: 28-02-19 19:19

Random sampling

Description- Every person in the target population has an equal chance of being selected. The researcher obtains a list of all the members in the target population and then use a computer as a random generator or “names out of a hat” technique to select the required number of participants.

-Free from researcher bias as they have no control over who gets selected.

-Time consuming.
-A representative sample is not guaranteed as there’s a chance some sub groups may be over represented or not selected.

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Systematic sampling

Description- when every nth member of the target population is selected a sampling frame (target population) is produced following by a sampling system (e.g. every 7th person) to obtain the sample.

-Free from researcher bias as they have no control over who gets selected so a fairly representative sample is obtained.

-Not entirely unbiased unless the number selected for sampling is chosen randomly.

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Stratified sampling

Description- This sample represents a composition of people in certain sub groups (strata) within the target population.

-If avoids researcher bias as the members selected from the sample are randomly selected and the sample represents the strata composition.

-It may lack a 100% representation as individual differences cannot be accounted for.

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Opportunity sampling

Description- The researcher selects anybody who is readily available and willing to take part.The researcher asks people its most convenient for such as a lecturer asking their students to take part in an experiment.

-Convenient method.
-Saves time and effort.

-unrepresentative of the target population.
-Suffers from researcher bias as the researcher has complete control over who gets selected.

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Volunteer sampling

Description- Participants put themselves forward as the researcher puts an advertisement in a magazine/newspaper, on the radio, on the internet/via email asking people to take part in research.They might put questionnaires somewhere public and get people to return their answers.

-Requires minimal input from the researcher.

-There’s volunteer bias as the most motivated and co-operative will respond.
-Only people who see the advertisement have a chance of being selected so affects the generalisability of the findings.

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