webpsy330 quasiexperimental group

8/13/2019 WEBPSY330 QuasiExperimental Group

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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 ora ______ 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 (non-

experimental)

4. Cross-sectional design (non-experimental)


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QUASI-

EXPERIMENTAL

NON-EXPERIMENTAL

Time-series design

(One group)

Differential/Causal comparativedesign

(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)

Summary of Quasi & Non-experimental designs


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When would you use a quasi-

experimental 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


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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 onproductivity in two factories

e.g., Effects of Home-based vs. School-based

treatment on problem behavior

Pretest-Posttest Nonequivalent Control-

Group Design


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Posttest Only (Static) Group Design


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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

Posttest Only (Static) Group Design


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____________Design

Intact Group of

Participants

Measurement

of DV

Measurement

of DV

Measurement

of DV

Measurement

of DV

Measurement

of DV

Experimental

Condition


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Time-Series Design

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SmokingFrequency

Before Campaign After Campaign

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SmokingFrequency

Intervention

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Smok

ingFrequency

Intervention

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Smok

ingFrequency

Intervention

Example: Effects of anti-smoking campaign on smoking frequency

No ______ group

hard to tell ifcampaign was effective

Time Series

Effect was just partof periodic ____________

Time Series Effect was just part

of downward ________

Time Series Effect occurs only

after ____________


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Developmental Research Designs

study age-related changes in behavior

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 _____, ________

Group at

Time 1

(e.g., 10 yrs)

Group at

Time 1

(e.g., 20 yrs)

Group at

Time 1

(e.g., 40 yrs)


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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

________________

webpsy330 quasiexperimental group

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