#9 Step 5: Non-experimental/Quasi Design

Question 1

Why use non-experimental/quasi design strategy?

Answer 1

1. Variables are difficult to manipulate (e.g. gender, age)

2. Manipulation/random assignment is unethical (e.g. depression)

Question 2

Disadvantages of non-experimental/quasi design

Answer 2

No experimental manipulation/control - difficult to establish unambiguous cause-and-effect relationships

Question 3

Types of non-experimental/quasi research strategies

Answer 3

1. Differential Research Design
2. Posttest-Only Non-Equivalent Control Group Design
3. Pretest-Posttest Design
4. Pretest-Posttest Non-Equivalent Control Group Design
5. Time-Series Design

Question 4

What is differential research design?

Answer 4

A research study that simply compares pre-existing groups with one another (no random assignment)

• Non-experimental
• ALWAYS a between-group experimental design

Question 5

What is posttest-only non-equivalent control group design?

Answer 5

A research study that uses pre-existing groups, one of which serves in the treatment condition and another in the control condition

• The goal is to evaluate the effectiveness of treatment administered to a pre-existing group of participants
• Non-equivalent because no random assignment (therefore subject to indiv differences)

Question 6

What is prettest-posttest design?

Answer 6

A research study that consists of one observation for each participant made before and after the treatment
- Similar to within-subject design, but no counterbalancing (used when it is impossible to carry out counterbalancing)

Question 7

What is pretest-posttest non-equivalent control group design?

Answer 7

A research study that consists of a pretest and a posttest for 2 nonequivalent groups. One group receives treatment, the other does not.

Question 8

Advantages/disadvantages of pretest-posttest non-equivalent control group design?

Answer 8

1. addition of pretest measures allows researches to address problem of individual differences (can confirm that any changes not because of pre-existing mathematical abilities)
2. allow researchers to examine whether the treatment or some other time-related factor is responsible for the changes
   - they are observed over the same amount of time

Disadvantage: without counterbalancing/random asg, there is the internal threat of time threats and differences (although better understood)

Question 9

Time-Series Design

Answer 9

A research study in which a series of observations are made for each participant before and after treatment/event

• event/outside occurrence = interrupted time-series design
• can see trends that already existed before treatment

Question 10

What are the 2 types of developmental research design?

Answer 10

1. Cross-Sectional Dvt Research Design: between-subject design that uses separate group of participants for each of the ages being compared
   - convenient and less costly
   - cohort effect (generational gap)
2. Longitudinal Dvt Research Design: a within-subject design that involves measuring a variable in the same group of individuals over a long period of time
   - absence of cohort effect
   - expensive and time-consuming
   - participant attrition