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Obtaining Research Participants

Obtaining Research Participants. With a few exceptions, most of the research questions that psychologists address are pertinent to broad groups of people. For example, consider the following question: Does warm or sensitive parenting promote the social competence of children?

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Obtaining Research Participants

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  1. Obtaining Research Participants • With a few exceptions, most of the research questions that psychologists address are pertinent to broad groups of people. • For example, consider the following question: Does warm or sensitive parenting promote the social competence of children? • The question is limited to parents and children, but doesn’t limit itself to specific cultures, sexes, etc. • The group of interest, then, might be said to be “children” in the broadest sense of the term.

  2. Populations • The group of people (or animals) that a research question pertains to is typically called the population. • In some cases, the population can be easily studied. Example: biographical studies of American presidents • In most real-world research scenarios, we cannot study the population per se. Instead, we typically study a subset of the population.

  3. Samples vs. Populations • The subset that is studied is typically called a sample. • In short, a sample is a subset of the population.  Population Sample There are a variety of methods for obtaining research samples

  4. Obtaining Research Samples • Accidental & Convenience sampling: the sample is acquired as a matter of convenience - first 100 people we meet on the street - college student volunteers - first 50 people who stop at our booth at the mall

  5. Obtaining Research Samples • Quota sampling: Deliberately creating a sample that matches the population on one or more known characteristics (e.g., age, sex, ethnicity)

  6. Obtaining Research Samples • Random sampling: each individual in the population has an equal chance of being selected

  7. Obtaining Research Samples • Random sampling is the only method that can, theoretically, ensure a representative sample Arepresentative sample has the same characteristics as the population. • Even though quota sampling methods yield samples that are representative with respect to some characteristics, quota sampling cannot guarantee that the sample will be representative with respect to all characteristics

  8. Class example of how random sampling works • Seat coordinates and sex [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] zx 3 6 8 1 13 7 9 8 7 6 zy 5 13 7 11 4 6 8 11 11 9 • Sampling error left to right front to back

  9. How many research subjects do you need to help ensure that the sample will be representative of the population?

  10. [,1] [,2] zx 7 12 zy 2 1 [,1] [,2] [,3] [,4] zx 10 5 12 10 zy 6 12 5 2 [,1] [,2] [,3] [,4] [,5] [,6] zx 7 3 10 11 3 2 zy 9 9 4 6 9 11 [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13] [,14] zx 3 9 11 9 12 6 11 10 12 1 7 11 6 4 zy 13 6 3 9 2 5 9 11 7 10 8 2 11 4 left to right : top row (zx) front to back : second row (zy)

  11. 40 zx 13 5 13 6 4 1 13 1 2 13 8 13 zy 4 7 7 11 6 8 7 6 9 10 5 6 zx 9 6 8 8 6 11 9 8 6 10 8 zy 5 6 3 5 5 8 6 9 2 7 5 zx 7 8 10 8 2 13 7 12 8 6 8 zy 8 2 10 10 1 11 5 2 3 3 1 zx 7 5 3 8 10 2 zy 1 6 9 9 2 1

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