History was only a minor problem in the study because
no unplanned event that might influence the postmeasurement
of the dependent variable occurred between
the pre-test and post-test measurement of the
dependent variable.
Maturation or ‘‘any physical or mental change that occurs
over time that affects performance on the dependent
variable’’ (Fraenkel and Wallen 2000, p. 236) was
controlled for in the current study.
Testing was only a minor problem in this study, as
problems can occur when participants respond to an
instrument more than once.
Regression artifacts were controlled for in the current
study since there was no tendency for very high scores to
become lower or very low scores to become higher
during post-testing.