Obtaining Research Participants

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 doesnt limit itself to specific cultures,
  sexes, etc.
• The population, 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

• 1. 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

• 2. 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

• 3. 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
• A representative 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
• gt rbind(zx, zy)
• ,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

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

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

12
(No Transcript)