Research Design


Uploaded by PSUClearinghouse on 26.01.2012

Transcript:
Hi, I'm Dr. Cameron Richardson, Research Scientist with the Clearinghouse for Military Family Readiness.
My background is in developmental psychology.
Before we begin, I'd like to thank my colleagues for their help in the development of this presentation. Let's begin.
Today we will be talking about the logic behind the use of control groups in your
research designs.
This podcast serves as a refresher session and as such we will see discussion of
other important aspects of studies design for future podcasts.
So let's get started.
I thought we'd talk about the logic of control groups using program evaluations
as our context.
And in this context, our goal is to be able to make conclusions about whether our
program did what it intended to do
that is assuming positive change in an outcome of interest we want to know
whether the change can be attributed to the program or not.
This is a deceptively simple goal
with one main hurdle to overcome in order to be able to make claims about
programs effects
and that is the elimination of alternative explanations.
Now I have one primary means of eliminating alternative explanations
and that is to identify and use comparable control
control groups
So let's say a program developer decides to market a special program of physical
activity claiming the physical activity will promote intelligence later in life
and she designs a study to measure intelligence three months and eighteen
years of age
and if you're wondering
that's a baby rattle with which the developer teach the infants to do bicep
curls
so with this example in mind remember that the goal of the research study as a
relates to this context
is to be able to say that the program caused the change in intelligence
and remember that the hurdle is all the potential alternative explanations that
could account for the change in intelligence
such as time spent reading
so it turns out that the developer reports the following results
those babies who received her special physical activity intervention
gained intelligence over time
while she's reporting the results she's beaming with joy because she thinks this
evidence is sufficient to conclude that her program worked
Much to her dismay you sit back and express your concern in the form of a
question
while you're data is intriguing mam whats to prevent me from arguing that it was
simply exposure to books that caused this change in intelligence
inwardly being at your good sense
you're shocked and outraged to hear that she cannot eliminate your alternative
explanation
meaning that we still don't know after eighteen years mind you
whether her program caused the change in intelligence
at this point with the program developer sweating it out her student steps in to
intervene admitting that she has without her advisors knowledge
run a concurrent study to utilize the comparable control group
for example similar SES same linguistic exposure
similar number of books in the household
And she reports the following results
those babies who received the special physical activity program showed more
gains in intelligence over time
than those babies without program
at this point you thinking up ways to approach the program developer student
because you're impressed with her savy
that is the students decision to include a comparable control group
allows more confidence in the conclusion that the program caused the change in
intelligence
because a comparable group that did not receive the physical activity program did
not fare as well so that's essentially it we want to use comparable control
groups so that we can compare apples to apples
said another way the control group serves as a natural reference group with
which to compare growth trajectories thus eliminating alternative
explanations for program effects
And what results as more confidence in conclusions about program effects
we've provided some references for further inquiry is the interest strikes you
beyond that I want to thank you for stopping in and remember that what we covered in the
session is just one component of a larger scientific process
i hope that you look for future podcasts on other related topics