Week 6: Quasi, N-of-1, Other Designs Flashcards
Quasi-experimental designs lack what
Random assignment, control group, or both
Time Series Design types
one-group pretest-posttest design
Repeated measures design
interrupted time series design
Single group designs have what as the independent variable
time
One-Group Pretest-posttest design
-all subjects have the same treatment
- no control group (limits in internal and external validity)
- IV is time
- IV has 2 levels
A One-Group Pretest-posttest design is defendable when
- the behavior of a control group has been documented
- ethical implications of withholding treatments
- time interval is very short
True experiments (RCTs) CAN have a pretest and a posttest BUT when change score are analyzed…
it removes time as an IV
Repeated Measures design is NOT a …
“true experiment”
Repeated Measures design has NO…
comparison (control) group
Interrupted Time Series Design (ITS)
- multiple DV measures
- interrupted by 1+ treatment occasions
- treatment does not vary
- IV is time
- no control group
Multiple measures within an ITS =
sudo-control
nonequivalent =
not formed by randomization
types of Nonequivalent Group Designs
- nonequivalent pretest-posttest control group design
- historical controls
- nonequivalent posttest-only control group design
Pretest-posttest design
- no random assignment
- intact groups
- subject preferences
(some control over threats to internal validity)
Historical Controls include
- received a different treatment during an earlier time period
- imbalance in characteristics of the groups
- hard to use information from other studies cause you can’t control the past study
Nonequivalent Posttest-only control group design
- no random assignment
- no pretest
- exploratory purposes NOT explanatory
Which design type has the most threats to validity
Nonequivalent posttest-only control group design