Chankon Kim
Ouasi-Experimental Designs, pp. 34-64, Campbell and Stanley

Guasi-experimental designs are applicable to settings where the experi-
menter has a perfect control over sceheduling of data collection proce-
dures (e.g., the when and the whom of measurement) but lacks the full
control over the scheduling of experimental stimuli (the when and to
whom of exposure and the ability to randomize exposures) which makes a
true experiment possible, This lack of control in guasi-experiment dic-
tates that one must in interpreting the results, consider in detail the
likelihood of uncontrolled factors accounting for the results. The more
implausible this becomes, the more valid the experiment. The designs in
general are believed to be sufficiently probing, however, to be well
worth employing where more efficient probes are unavailable.

7, lTime-Series Experiment
O, 02 O3 O4a X Op O0e O, Og

The essence of the time-series design is the presence of a periodic mea-
surement process on some group or individual and the introduction of an
experimental change into this time series of measurements the results of
which are indicated by a discontinuity in the measurements recorded in :
the time series. The test of significance in the effect of X concerns in-
tercept and slope of the time series measurements before and after the
treatment - test of linear fit to the data.

8. Eguivalent Time-Samples Design
X,;0 X50 X;0 X,0

The design can be seen as a form of the time series experiment with the
repeated introduction of the experimental variable, and is most useful
where the effect of the experimental variable is anticipated to be tran-
sient or reversible character.

Tests of significance deals with two dimensions of generalization: across
occasions and across persons. If only one or two repetitions of each ex-
perimental condition are involved, sampling errors of occasions may be .
large or the control of history will be poor. Generalization across per-
sons depends on the size and the representativeness of the sample. T-test
or ANOVA may be used to test significance.

9 Eguivalent Materials Design