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19 Cards in this Set
- Front
- Back
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random assignment to a group, involves the distribution of subjects to either an experimental or control group
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Randomization
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- the introduction of one or more constants into the experimental situation
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control
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the provision of some experimental treatment, in one or varying degrees, to some of the subjects to the study
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manipulation
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randomization, control, manipulation. level 2
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true exp. design
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pretest-post control group design
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True experiment
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has 2 groups that are identical to those used in classic experimental design, plus 2 additional groups; an experimental after-group & a control after-group
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Solomon four-group design
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posttest only control group design, is composed of 2 randomly assigned groups, but unlike the true experimental design, neither group is pretested or measured
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After-only design
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Threat to internal validity: mortality of second group & testing b/c same measurement used twice
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True or Classic Experiment
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2 groups that are identical to those used in classic experimental design, plus 2 additional groups (exp after-group & control after-group)
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Solomon four-group design
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internal validity threat: testing, mortality
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Solomon four-group design
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Posttest only; composed of 2 randomly assigned groups, but unlike true exp design, neither groups is pretested or measured
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After-only Experimental Design
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Don’t know where they start
Useful when testing effects are expected to be major problem, when outcomes can’t be measured beforehand, & when # available subjects is too limited to use Solomon 4 group design |
After-only Experimental Design
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Design in which the researcher initiates an experimental treatment, but some characteristic of a true experiment is lacking
(e.g. no control group or no randomization) Internal validity may be compromised, & ability to determine treatment caused changes observed in outcome is weakened Weakened confidence in making causal assertions Level III evidence Intended to test cause-and-effect relationships |
Quasiexperimental Designs
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Nonequivalent control group design
After-only nonequivalent control group design One group (pretest-posttest) design Time series design |
Types of Quasiexperimental Designs
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Experimental group
O1 X1 O2 Control group O1 O2 Problem: No randomization Used in studies conducted in field setting Weakened confidence assuming experimental & comparison groups are similar at beg of study Threats to internal validity: selection, maturation, testing, & mortality Strong b/c gathering of data at time of pretest |
Nonequivalent control group design
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Experimental group
X O2 Control group O2 No Randomization |
After-only (non)Equivalent Control Group Design
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Experimental group
O1 X O2 No Randomization, No control group When only 1 group available |
One Group (pretest-posttest) Design
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Experimental group
(pre-tests) (post-tests) O1 O2 O3 O 4 X O5 O6 O7 O8 No randomization, No control Threats to internal validity: testing, mortality, maturation, selection Determine trends |
Time Series Design
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Practical, feasible, & generalizable
May be only way to evaluate the effect of IV of interest **** Cannot make clear cause-and-effect statements |
Advantages & Disadvantages of Quasiexperimental Design
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