RESEARCH DESIGNS
IV = Intervention occurs (the level of the independent variable is changed) DV = Dependent variable t_{n} = Time of measurement of DV X = Experimental group C = Control group
Desirable features in research designs:
1. Premeasure the dependent variable 2. Experimenter controls or applies the intervention (independent variable) 3. Use control group, with random assignment (best) or matching
EXPERIMENTAL DESIGNS
Beforeandafter (classic experiment)
Every desirable feature
(X) DVt_{1}…......IV.......DVt_{2} (C) DVt_{1}…….........…DVt_{2}
Solomon fourgroup design
Even better  checks for effects of premeasure (X_{1}) DVt_{1} …. IV.…..DV t_{2 } (C_{1}) DVt_{1} ………… DV t_{2} (X_{2})....……... IV...... DV t_{2 } (C_{2})....……………...DV t_{2}
Effect of the intervention: (X[DVt_{1}XDVt_{2}]) – (C[DVt_{1}CDVt_{2}])
Experimental panel design (interviews) or "interrupted timeseries" design
Longitudinal equivalent of the classic experiment. Dependent variable measures can reflect interview responses or other data (e.g., crime rate)
(X) DVt_{1}…IV…......DVt_{2}…......DVt_{3}…......DVt_{4} (C) DVt1………......DVt_{2}…......DVt_{3}…......DVt_{4}
QUASIEXPERIMENTAL DESIGNS
Beforeandafter, but lack a control group, or use a control group that is not matched or randomized
DVt_{1}….....IV…......DVt_{2}
Same, but design is a "panel" (dependent variable reflects interviews) or a "timeseries" (dependent variable measured several times)
DVt_{1}…....IV…......DVt_{2}….....DVt_{3}….....DVt_{4}
Afteronly, with or without a control group
No measure of the DV was taken before the independent variable was applied
With control group
(X) IV…DV t_{2} (C) IV…DV t_{2}
Without control group
IV…DV t_{2}
Nonexperimental design that mimics an experiment
 A known "intervention"  the independent variable was adjusted on a certain date
 There are measures of the dependent variable before and after the date
 Preferable  a control group that closely matches the characteristics of the experimental group can be identified
NONEXPERIMENTAL DESIGNS
Investigator does not adjust the independent variable.
Expost facto/"passive statistical"
Most common type of CJ research, where both the dependent variable (DV) and independent variable (IV) are measured retrospectively (after the fact).
Crosssectional
Subgroups of the independent variable (e.g., gender) are separately assessed for their effect on the dependent variable.
Panel or time design
Repeated interviews of the same group of subjects over time, or repeated measurement of a single characteristic over time (e.g., crime rate). These are often called "cohort" studies.
T_{1}…T_{2}…T_{3}…T_{4}
Multiplegroup trend
Larger group is broken down into matched or randomly drawn subgroups, and each is interviewed once over time. The goal is to control for the influence of the measurement process.
subgroup1 T_{1} subgroup 2 T_{2} subgroup 3 T_{3} subgroup 4 T_{4}
