Page 169 - [Uma_Sekaran]_Research_methods_for_business__a_sk(BookZZ.org)

FACTORS AFFECTING INTERNAL VALIDITY 153

Figure 7.2
Illustration of maturation effects on cause-and-effect relationship.
Time: t 1 t 2 t 3

Independent variable Dependent variable

Enhanced technology Efficiency increases

Gaining experience and
doing the job faster

Maturation effects

Testing Effects
Frequently, to test the effects of a treatment, subjects are given what is called a
pretest (say, a short questionnaire eliciting their feelings and attitudes). That is,
first a measure of the dependent variable is taken (the pretest), then the treat-
ment given, and after that a second test, called the posttest, administered. The dif-
ference between the posttest and the pretest scores is then attributed to the
treatment. However, the very fact that respondents were exposed to the pretest
might influence their responses on the posttest, which would adversely impact
on internal validity.
For example, if a challenging job is expected to cause increases in job satisfac-
tion, and a pretest on job satisfaction is administered asking for employees’ level
of satisfaction with their current jobs, it might sensitize people to the issue of job
satisfaction. When a challenging job is introduced and a further job satisfaction
questionnaire administered subsequently, the respondents might now react and
respond to the posttest with a different frame of reference than if they had not orig-
inally been sensitized to the issue of job satisfaction through the pretest.
This kind of sensitization through previous testing is called the testing effect,
which also affects the internal validity of experimental designs. In the above
case, though increases in job satisfaction can legitimately be measured through
pre- and posttests, the pretest could confound the cause-and-effect relationship
by sensitizing the respondents to the posttest. Thus, testing effects are another
threat to internal validity.

Instrumentation Effects
Instrumentation effects are yet another source of threat to internal validity. These
might arise because of a change in the measuring instrument between pretest and
posttest, and not because of the treatment’s differential impact at the end (Cook
& Campbell, 1979a). For instance, an observer who is involved in observing a
particular pattern of behaviors in respondents before a treatment might start