Sampling

Question 1

What is a population?

Answer 1

all individuals that are there (usually too big to test every individual)

Question 2

What is a sample?

Answer 2

a smaller group chosen from big group

Question 3

What is generalization?

Answer 3

applying findings from a sample to a large population

Question 4

Representative Sample

Answer 4

matches characteristics of the population

Question 5

Non-Representative Sample

Answer 5

biased

Question 6

Random sample

Answer 6

identify the population and then draw a random sample from it

Question 7

Nonrandom sample

Answer 7

choosing special individuals/ subject pools
Only university students
Internet research
Animal subjects (same breed, sex etc.)

Question 8

Simple Random sampling

Answer 8

randomly selecting a number of people

Question 9

Stratified sample

Answer 9

dividing population into segments (=strata), then selecting a sample of equal size from each segment

Question 10

Proportionate Sampling

Answer 10

proportions of people in the population are equal to proportions in your sample

Question 11

Systematic sampling

Answer 11

every Kth element after a random start

Question 12

Cluster sampling

Answer 12

naturally occurring groups of subjects and randomly selecting certain clusters
• Multistage sampling: selecting individuals from those clusters

Question 13

What are characteristics of laboratory research?

Answer 13

• Take individuals into laboratory setting
• Control variables
• More ethical
• High internal validity and low external
validity (discussed next week)

Question 14

What are characteristics of field research?

Answer 14

• In participants natural environment
• Lesser control of confounding variables
• Results can easily be generalized to the real
world
• High external validity and low internal
validity

Question 15

Things to consider for research setting (ethics, bias, validity?)

Answer 15

• In participants natural environment
• Lesser control of confounding variables
• Results can easily be generalized to the real
world
• High external validity and low internal
validity

Question 16

What is internal validity?

Answer 16

• Ability of your research design to adequately test your hypothesis
• Showing that the variation in the independent variable caused the observed effect

Question 17

What are threats for internal validity?

Answer 17

• Rival hypothesis: another alternative variable might explain the effect
• Confounding: combination of variables explains the effect and one cannot separate the effect of these variables

Question 18

What are sources of confounding?

Answer 18

• History: specific events other than treatment occur between observations
• Maturation: fatigue or aging change performance over time
• Instrumentation: instrument calibration changes and confounds the effect
• Statistical regression: subjects selected for treatment on the basis of their extreme scores tend to move closer to the mean when retesting
• Biased subject selection: nonrandom
• Experimental mortality: dropouts
• Demand characteristics: participants know
the purpose of the study and behave differently

Question 19

What is external validity?

Answer 19

• ability of your research design to generalize the results beyond the research setting to real world situations

Question 20

External vs. Internal validity

Answer 20

• Usually an increase in one means a decrease in other→find compromise
• Theoretical problems: internal
• Real World problems: external

Question 21

What are threats to external validity?

Answer 21

• Reactive Testing: pretests may affect reaction to the experimental test
• Interactions between participant selection biases and the independent variable: participants that signed up voluntarily could be more extroverted, this could affect your study if you are measuring for example personality types
• Reactive effects of experimental arrangements: artificial experimental setting and knowledge of being a study-participant change results
• Multiple treatment interference: If participants are exposed to multiple treatments and later treatments are affected by former ones

Question 22

Exam question:

Which of these threaten internal Validity?
I. History
II. Statistical Regression

A. Both I and II are threats.
B. Only I is a threat.
C. Only II is a threat.
D. Both I and II are threats to external validity, but not internal validity.

Answer 22

Answer: A