Quasi & Non-Experimental Designs
Quasi-Experimental designs: Not quite true experiments
because the different groups/conditions are not
created by __________________. Groups or
conditions are defined by _____________ variable or
a ______ variable.
Non-Experimental designs – do not allow you to rule out
many threats to _______________.
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Quasi & Non-Experimental Designs
Those using ____ group, compare behavior across _____:
• Time-series designs (quasi-experimental)
• One group pretest-posttest (non-experimental)
• Longitudinal design (non-experimental
Those using multiple, ____________ groups:
1. Pretest-posttest nonequivalent control group design
(quasi-experimental)
2. Posttest-only control group design (Static-group design)
(non-experimental)
3. Differential (Causal-comparative) design (nonexperimental)
4. Cross-sectional design (non-experimental)
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Summary of Quasi & Non-experimental designs
QUASIEXPERIMENTAL
NON-EXPERIMENTAL
Time-series design
(One group)
Differential/Causal comparative
design
(Multiple groups)
Pretest-posttest non-equivalent
control-group design
(Multiple groups)
Developmental: Cross Sectional
design
(Multiple groups)
Developmental: Longitudinal design
(One group)
One-group pretest-posttest design
(One group)
Posttest-only nonequivalent group
(Static) design
(Multiple groups)
When would you use a quasiexperimental design?


When you want to investigate a relationship but cannot
create ________ assign groups
It is not _________ to create randomly assigned groups
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Pretest-Posttest Non-Equivalent Control-Group
Design
Pretest-Posttest Nonequivalent ControlGroup Design



Definition: A quasi-experimental design in which behavior
in two _______________groups is measured pre and
post-IV
No random __________ and ___________
Because you measure behavior before treatment you can
evaluate group equivalence - it reduces the threat of
_______________

e.g., Effects of Flexible vs. fixed work hours on
productivity in two factories

e.g., Effects of Home-based vs. School-based
treatment on problem behavior
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Posttest Only (Static) Group Design
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Posttest Only (Static) Group Design




No random selection and assignment
2 __________________, e.g., children in 2 clinics
Groups should be ______
Susceptible to internal validity threats, e.g., assignment
bias (selection threat) - group assignment is _______

Example: effects of peer tutoring in two classrooms
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Time-Series Design





Definition: A quasi experimental design in which
behavior in one group of participants is measured
across time _______________ an IV is implemented.
___________________ control for multiple threats to
internal validity
Allows you to evaluate _________ across time
Called ___________________ when the IV is not
created by the experimenter
Called a time series design with _______________if the
treatment is repeatedly presented across multiple
groups.
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Intact Group of
Participants
Measurement
of DV
Measurement
of DV
Measurement
of DV
____________
Design
Experimental
Condition
Measurement
of DV
Measurement
of DV
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Time-Series Design
45
40
Smoking Frequency
Smoking Frequency
Example: Effects of anti-smoking campaign on smoking frequency
35
30
25
20
15
10
5
0
Before Campaign
35
30
25
20
15
10
5
0
After Campaign
No ______ group – hard to tell if
campaign was effective
45
40
Intervention
Time Series – Effect was just part
of periodic ____________
Smoking Frequency
Smoking Frequency
45
40
35
30
25
20
15
10
5
0
Intervention
Time Series – Effect was just part
of downward ________
45
40
35
30
25
20
15
10
5
0
Intervention
Time Series – Effect occurs only
after ____________
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Developmental Research Designs –
study age-related changes in behavior
Group at
Time 1
(e.g., 10 yrs)
Group at
Time 1
(e.g., 20 yrs)
Group at
Time 1
(e.g., 40 yrs)
Longitudinal design
 Measuring a variable in individuals over an
___________________
 Like a time-series design with no
_______________
 Can determine how an individual _________
 No cohort effects
 Very _____________, expensive
 Problems with _____, ________
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One-Group Pretest-Posttest
Design
1 naturally occurring group
Pretest and postest
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One Group Pretest-Posttest Design


Observation made in ____ group before and after
treatment
No attempt is made to control for many threats to
________________
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