Quiz 2 Material

Question 1

Using your own words, define internal validity

Answer 1

Internal validity is the level of assurance that the changes to the independent variable cause the results of the dependent variable.

Question 2

Using your own words, define external validity

Answer 2

External validity is the extent to which the results of the study can be applied to the population of interest.

Question 3

List and, in your own words, briefly describe each of the threats to internal validity

Answer 3

History: over time possibility something is happening simultaneously causing an effects other than the treatment
Maturation: over time natural changes may effect the data (ie children, sunlight)
Testing: with repetition the second is likely to be better because of practice
Instrumentation: All data errors from instruments
Statistical regression: groups formed by extreme scores and with a second test data regresses to an average
Selection bias: participant groups not randomly assigned
Experimental mortality: participants pull out for any reason
Selection-maturation interaction: Over time, groups by ages may be aging process influenced differently
Expectancy: measurements not taken objectively

Question 4

List and, in your own words, briefly describe each of the threats to external validity

Answer 4

Interaction effect of testing: pretest may motivate participants
Interaction of selection bias and experimental treatment: sample does not represent population
Reactive effects of experimental setting: not being in normal environment effects performance
Multiple-treatment interference: Participants perform differently on the second test because of the first test.