Chapter 5: Selecting Research Participants

Question 1

Sampling

Answer 1

The process by which a researcher selects participants for a study.

Question 2

Probability Sample

Answer 2

A sample that is selected such that the likelihood that any particular individual in the population will be selected for the sample can be identified.

Question 3

Simple Random Sample

Answer 3

Most common probability sample; every possible sample of the desired size has the same chance of being selected from the population.

Question 4

Representative Sample

Answer 4

A sample from which we can draw accurate, unbiased estimates of the characteristics of the population.

Question 5

Sampling Error

Answer 5

The extent to which characteristics of individuals seleced for the sample differ from those of the population.

Question 6

Error of Estimation

Answer 6

Indicates the degree to which the data obtained from the sample are expected to deviate from the population.

Question 7

What three things is the error of estimation a function of?

Answer 7

1. Sample Size
2. Population Size
3. Variance of the Data

Question 8

Data obtained from a sample will be more similar to the population when…?

Answer 8

1. The sample is larger
2. The population size is smaller
3. The error variance in the data is smaller

Question 9

Systematic Sampling

Answer 9

Involves taking every so many individuals for the sample (e.g. interview every 8th person that comes into the emergency room).

Question 10

Stratified Random Sampling

Answer 10

The population is divided into strata, then participants are randomly selected from each stratum. (i.e. a subset of the population that shares a particular characteristic such as gender, race, or location).

Question 11

Cluster Sampling

Answer 11

Sampling groups or clusters of participants; clusters are based on naturally occurring groups that are usually in close proximity.

Question 12

Nonresponse Problem

Answer 12

Failure to obtain responses from individuals that researchers select for the sample.

Question 13

Misgeneralization

Answer 13

Occurs when a researcher generalizes the results to a population that differs from the one from which the sample was drawn.

Question 14

Convenience Sampling

Answer 14

Using whatever participants are readily available; researchers often use convenience samples of college students.

Question 15

Quota Sampling

Answer 15

Convenience sample in which the researcher takes steps to ensure that certain kinds of participants are obtained in particular proportions (e.g. a researcher may wish to obtain an equal number of men and women).

Question 16

Purposive Sampling

Answer 16

Researchers use their judgment to decide which participants to include in the sample, trying to choose respondents who are typical of the population.

Question 17

Economic Sample

Answer 17

A sample that provides a reasonably accurate estimate of the population at reasonable effort and cost.

Question 18

Power

Answer 18

The ability of a research design to detect any effects of the variables being studied that exist in the data (i.e. the probability that the test will correctly reject a false null hypothesis).

Question 19

Power is increased with…?

Answer 19

1. Larger effect sizes
2. Larger sample sizes
3. Larger (less stringent) alpha levels
4. One-tailed (instead of two-tailed) tests

Question 20

What power is adequate?

Answer 20

Power of .80 (80% chance of detecting an effect) is generally considered desirable. In psychology, however, average power levels are about .20 for detecting small effect sizes and between .50 - .60 for detecting medium effect sizes.