1. Reply to: In an experiment, one of the most important
Reply to: In an experiment, one of the most important things a researcher must focus on is
the principle of validity, or the assurance that the research is actually studying what it was
intended to study (Myers & Hansen, 2012). When setting up an experiment, there are two
forms of validity in particular that the researcher must focus one. Firstly, the researcher
must focus on internal validity. This type of validity is concerned with the assurance that
the changes that were measured in the dependent variable (DV) were actually caused by the
manipulation of the independent variable (IV) and not caused by any other types of
extraneous variables (EV). Secondly, researchers must be concerned with their study’s
external validity. External validity refers to how well the results of the study generalize to
the population of interest from which the sample was pulled (Myers & Hansen, 2012). When
setting up an experiment, there are several ways in which the researcher can increase both
of these validity types.For internal validity, one of the main concerns is the study’s amount
of control. Control refers to the number of safeguards that were put in place in order to
control for EV’s, or variables other than the IV that may have influenced or changed, the DV
(Myers & Hansen, 2012). The best time to plan for these controls is during the set up of the
experimental procedures. For example, researchers should ensure that they have properly
defined their variables, properly set up their measuring techniques, and included enough
levels of the IV to properly test their hypothesis. Additionally, in order to control for EV’s
caused by subject variables, or individual differences between subjects, researchers should
ensure they utilize random assignment (Myers & Hansen, 2012). Researchers can also
choose to measure their internal validity after their study is over. For example, researchers
can provide questionnaires, or surveys, to their subjects after the study concludes in order
to investigate how the subject felt during the examination, or if they were confused during
the study. These are important factors to look at as these could introduce possible EVs into
the study that may have resulted in the measured behaviors (Myers & Hansen, 2012).As
mentioned above, the primary concern for external validity is the generalizability of the
identified experimental results (Myers & Hansen, 2012). External validity has a type of
double-edged sword type of relationship with the previously discussed principle of internal
validity. For example, as internal validity increases with the number of controls put in place,
external validity decreases with large amounts of controls as it is thought to limit realistic
behavior. There are several ways in which research can increase their studies external
validity. For example, researchers can use the principle of aggregation, or the grouping
together of data, subjects, stimulus, or trials (Myers & Hansen, 2012). The idea behind this is
2. that by aggregating these factors, they are generalizing the behaviors over a wide range of
subjects, stimuli, and occasions. This provides for the most realistic measure of behavior.
Additionally, researchers can choose to incorporate multivariate designs, or designs that
include multiple dependent variables (Myers & Hansen, 2012). The idea behind multivariate
designs is that rarely do behaviors exist independently. By measuring multiple DVs, or
behaviors, researchers can gather a more accurate representation of how the manipulated
IV actually impacted behavior. Lastly, researchers can maximize external validity by
designing experiments to minimize reactivity, or the tendency for subjects to change their
behavior when they feel as though they are being watched (Myers & Hansen, 2012). It is a
major belief that lab settings, or settings in which the behavior is overly controlled, does not
elicit realistic behaviors. With that in mind, researchers often try to maximize the measure
of behavior in more natural settings such as in field experiments or in naturalistic
observations (Myers & Hansen, 2012).
