Unit 10: Quasi Experimentation

Question 1

quasi experiments

Answer 1

The researcher selects participants from pre-existing groups (does not have control over assigning subjects to conditions).
Sometimes called ex post facto because assignment happens after the groups have formed (ex. male/female)
Difference between groups may not be the cause of the effect, could be obscuring the effect.

Question 2

non-equivalent control group designs

Answer 2

Experiment with a control and experimental group, but P are nor randomly assigned to them.

Question 3

repeated treatment designs

Answer 3

A design that attempts to improve validity by introducing the treatment more than once (return to baseline in between).

Question 4

interrupted time-series designs

Answer 4

A design that considers the trend before and after the experiment, so one group can be tested alone (no control)

Question 5

program evaluation

Answer 5

A set of techniques for determining the effectiveness of a social service program.

Question 6

summative evaluation

Answer 6

A way to determine whether a program is functioning adequately, meeting its goals.
Often after completion.
Can be used to determine cutbacks, changes, expanding, etc.

Question 7

formative evaluation

Answer 7

The goal is to improve the program.

Question 8

cross-sectional study

Answer 8

A design that tests different age groups at the same time to determine age-based differences.

Question 9

longitudinal study

Answer 9

A design that follows one P/group and tests them at different points over time to determine age-based differences.

Question 10

cross-sequential design

Answer 10

Tests 2+ groups at 2+ times to control for cohort effects, secular effects.

Question 11

Cohort effect

Answer 11

Effects of characteristics that are specific to a cohort.

Question 12

secular effect

Answer 12

Effects due to changes in the larger population/social environment.

Question 13

How are quasi experiments different from true experiments?

Answer 13

Still intend to show cause-effect, but one of these is not met:

1. researcher randomly assigns P to 2 groups that are roughly equivalent
2. researcher manipulates the IV
3. there is a control or baseline condition to compare to experimental/treatment condition

Question 14

Under what circumstances can quasi experiments be a useful tool?

Answer 14

• when only option/better than nothing
• when can’t practically or ethically assign P to groups for exposure to the IV
• can test lab results for external validity
• can suggest further research for lab
• can have higher external validity than true if more closely resembles the real world

Question 15

What is the major weakness of quasi experiments?

Answer 15

Confounding variables. Because the researcher doesn’t have complete control over assigning P to conditions. Difference between groups could be the cause of effect, or could be obscuring the real cause.

Question 16

Major threats in field testing (need to the diligent about these in quasi-experiments)

Answer 16

1. diffusion/imitation of treatment - groups share info/resources with each other - reduces difference
2. compensatory equalization - workers give treatment to control P - reduces differences
3. compensatory rivalry - disadvantaged group is motivated to perform better - reduces difference
4. resentful demoralization - disadvantaged group is discouraged and performs worse - increases difference

Question 17

What is a non-equivalent control group design with pretest and post-test? Under what circumstances are the results of quasi-experiments that use this design interpretable?

Answer 17

Control and experimental groups are not roughly equal - they differ in some way.
Add in a pre-test and post-test and then compare results.
The results are interpretable if they can be attributed to the difference between groups.
Pre-test scores start similar, then experimental change but control not, OR experimental starts lower and ends up higher.

Question 18

Under what circumstances is an interrupted time-series design useful?

Answer 18

When no control group is possible.

When data for before and after can be accessed to show trends.

Question 19

What different strategies are used in non-equivalent control group designs and interrupted time-series designs to control for confounding variables?

Answer 19

1. comparing pre- and post-test results with other groups

2. considering trends before and after the test

Question 20

What are repeated-treatment designs? How do these designs control for confounding variables?

Answer 20

The treatment is introduced multiple times, with a return to baseline between each. If the effect is consistent each time, it increases confidence that the IV is causing the effect in the DV. Proves the effect isn’t due to a trend.

Question 21

Which quasi-experimental designs can be used with a single subject (an individual, a company, or some other units)?

Answer 21

• interrupted time series
• repeated treatments
• longitudinal

Question 22

What are the common quasi-experimental designs used in developmental psychology?

Answer 22

• longitudinal
• cross-sectional
• cross-sequential

Question 23

advantages and disadvantages of Cross-sectional study

Answer 23

A: faster/cheaper, done by one researcher
D: hard to control for cohort effects, age is confounded with DOB.

Question 24

advantages and disadvantages of Longitudinal study

Answer 24

A: avoids cohort effects
D: takes longer, more expensive, more than one researcher, confounds age with time of testing (secular effects)

Question 25

advantages and disadvantages of Cross-sequential design

Answer 25

A: addresses the confounding in cross-sectional and longitudinal. Shows secular effects, though does not control for them.

Question 26

How can quasi-experimental designs be used in evaluations of social programmes?

Answer 26

They are useful because P are often assigned (not randomly) to groups. Comparing existing groups according to an IV requires a quasi-experimental design.