Lecture 4- Experimental Designs

Question 1

What is an experimental research design?

Answer 1

• Contains one or more factor that is manipulated or controlled (independent variable, IV)
• Contains one or more factor that is measured or observed (dependent variable, DV)
• Ideally, this design establishes that the IV is the cause of the DV

Question 2

What is a quasi-experiment?

Answer 2

• IV and participants are not randomly assigned
• Weaker evidence for casual conclusions
• Manipulate the IV, but can’t/don’t randomly assign participants to groups or conditions
• More susceptible to threats to internal and external validity

Question 3

What is a factorial design?

Answer 3

• May include both true and quasi-experimental components
• Consider a true experiment if even 1 IV meets criteria, but strong causal evidence only for the true manipulation
• Multiple IVs examined in 1 design

Question 4

What is a no-treatment control (posttest only: randomized treatment groups)?

Answer 4

• Participants are randomly put into 2 groups
• Then a treatment (X) or no treatment is applied to both groups
• Then 2 observations are recorded for each group

Question 5

What is an alternative treatment control (posttest only: randomized treatment groups)?

Answer 5

Similar to no-treatment control, but there are 2 different methods applied to the groups

Question 6

What is a pretest-posttest: randomized control group design?

Answer 6

• Participants are randomly assigned to 2 groups
• Observation (pretest) before the treatment is introduced
• Then observation following the treatment or no-treatment

Question 7

What is a solomon randomized four-group design?

Answer 7

Can calculate the impact of test-retest

Question 8

What is a nonequivalent control group design?

Answer 8

• Compare intact groups (e.g., classrooms)

- Typically pretest-posttest

Question 9

What are repeated measures?

Answer 9

• AKA within subjects design
• 2 or more measures from the same individual
• May be experimental (e.g., group) or non-experimental (e.g., time)
• Measurements may either occur within a particular session or across multiple sessions

Question 10

What is counterbalancing?

Answer 10

• Design to avoid order effects

- Randomly assign participants to a given order

Question 11

What is a single-subject design?

Answer 11

• AKA single case
• Not necessarily conducted on a single participant, but the data are presented in terms of individuals rather than groups
• Repeated measures
• Lacks random assignment

Question 12

What is a treatment withdrawl design?

Answer 12

AKA reversal design

A1-B-A2
- Applying a treatment and then withdrawing it

Question 13

What is a treatment reapplication?

Answer 13

A1-B1-A2-B2

- What if the participant doesn’t return to baseline?

Question 14

What is multiple treatment?

Answer 14

A1-B1-A2-C-A3

• Draw conclusions about B, but note that C always appears after B (serial order confound)

Question 15

What are multiple baselines?

Answer 15

Observe 2+ behaviors

• One you want to treat first
• One you will treat differently

Across participants:

• Balance treatment orders across more than one individual
• Deals with carryover effects

Question 16

What is internal validity?

Answer 16

Extent to which conclusions about cause-effect relationships are accurate

Question 17

How is history a threat to internal validity?

Answer 17

Outside events that influence participants in the course of the experiment or between repeated measures of the DV

Question 18

How is maturation a threat to internal validity?

Answer 18

Participants may change in the course of the experiment or between repeated measures of the DV due to the passage of time

Question 19

How is statistical regression a threat to internal validity?

Answer 19

Participants selected may perform very poorly on a test. However, participants with extreme scores on a first measure of the DV tend to have scores closer to the mean on a second measure.

Extreme scores are more likely to occur via chance.

Question 20

How is instrumentation a threat to internal validity?

Answer 20

The reliability of the instrument used to gauge the DV or manipulate the IV may change over the course of an experiment

Question 21

How is selection a threat to internal validity?

Answer 21

Groups differ in a systematic, non-random way prior to a study

Question 22

How is mortality a threat to internal validity?

Answer 22

In the course of an experiment, some subjects may drop out before it is completed (attrition).

Particularly problematic if the reason for dropping out is non-random

Question 23

What is the Rosenthal Effect?

Answer 23

Researcher sets up expectations (intentionally or unintentionally)

Question 24

What is a single blind study?

Answer 24

Participants don’t know what group they’re in

Question 25

What is a double-blind study?

Answer 25

Participant and researcher don’t know what groups the participants are in

Question 26

What is a triple blind study?

Answer 26

Participant and researcher and person scoring the data don’t know the participant groups

Question 27

What is the placebo effect?

Answer 27

Positive effect simply due to believing you’ve received treatment

Question 28

What is the nocebo effect?

Answer 28

Negative effect simply due to believing you’ve received treatment

Question 29

What is the Hawthorne effect?

Answer 29

Behavior changes just because individuals know they are being studied