LogoType
SOLVING PROBLEMS
CONTROLLING EXTRANEOUS
VARIABLES
SUBTOPICS
01
PERSONITY VARIABLES
VOLUNTEER SUBJECTS
02
CONTEXT VARIABLES
.WHEN THE SUBJECTS SELECT THE
EXPERIMENT
03
WHEN THE EXPERIMENTER SELECTS THE
. SUBJECT
04
SOME FOLKORE ABOUT SUBJECTS
Personality Variables
Personality Variable
Experimenter
“
“
Aside from the social variables and the qualities of the
relationships between subjects and experimenters, the
personal characteristics known as personality variables,
that an experimenter brings to the experimental setting can
be important too.
Personality Variable
Experimenter
“
“
Personality variable refers to the type of
personality the experimenter has that may
affect the subjects’ responses.
Personality Variable
Experimenter
“
There is a difference between the responses of subjects
when an experimenter is friendly and warm compared to an
experimenter who is cold and aloof.
“
Personality Variable
Experimenter
“
“
A response set called social desirability, experimenters
who score high on the social desirability scale are
particularly good at being likeable experimenters.
Personality Variable
Experimenter
It is important to maintain consistency in interactions with
subjects.
“
“
Personality Variable
Experimenter
“
The more the experimenter varies his behaviour, the more
he is likely to produce variability in the subjects’ responses.
The more variability is the subjects’ responses, the harder
it will be to detect the effect of the dependent variable.
“
Personality Variable
To reduce the influence of personality variable
“
a. use multiple experimenters and make sure that each exp
erimenter runs about the same number of people in each of
the conditions of the experiment
“
b. the best control is to keep face-to-face contact minimum
and adhere strictly to the experimental procedures
Volunteers Subjects
Volunteers Subjects
Random assignment makes this less
of a concern
“
“
Volunteers Subjects
Want the subjects personality to be a
representative of the population
“
“
Context Variables
Context Variables
“
“
Context Variables are those that come about
from procedures created by the
environment, or context, of the research
setting
Context Variables
“
“
Context Variables include subject recruitment,
selections, and assignments procedures, as
well as typical problems encountered in
research on a university population
When the subjects select
the experimenter
When the subjects select the experimenter
“
“
When you run an experiment using human subjects, you
may be allowed to recruit your subjects from a Subject
pool of Psychology Students
When the subjects select the experimenter
“
Most Departments of Psychology in major
universities rely on students who serve as res
earch subjects from time to time.
“
When the subjects select the experimenter
“
At research universities, Psychology students are
typically required either
 To Participate in a certain number of experiments
 To fill substitute requirement
“
When the subjects select the experimenter
In finding the subjects; there is a list of experiments
needing subjects posted on a WEBSITE or in a Central
location on campus
When the subjects select the experimenter
But sometimes students can sign up for a session on the spot!
Students can often look over what is available, select one that
seems interesting and make an appointment to participate
When the subjects select the experimenter
Factors involved in the decision:
Am I free at a time when subjects are needed?
What kind of Experiment is it?
Often, the only information that potential subjects are given is the
name of the experiment.
But sometimes, the titles can bias your sample, in which this reduces
the external validity of your experiment
When the subjects select the experimenter
So to avoid biased samples, researchers try to keep names NEUTRAL as
possible “without sounding boring” such as:
The Information Formation Experiment
The Close Relationship Experiment
Instead of “The Sexual Practices Survey”, a questionnaire study could be called
“Contemporary Judgements”.
Why do all of these?
Biased sample = Greatly reducing your ability to generalize your findings
And the experiment will have less external validity
When the subjects select the experimenter
The time for subjects to decide not to participate in your experiment. If
that happens, after the experiment is/has been explained to them at the
beginning of the session.
Therefore, always keep a record of subjects who “DROP OUT” and
what conditions of the experiment they were assigned to for your resear
ch report, even though it is unlikely that your experiment will include con
dition that are noxious enough to produce a subject “mortality threat”
When the subjects select the experimenter
Keep in mind that some subjects who volunteer will probably miss their
sessions for a variety of reasons such as:
 Friday sessions (notorious for No-Shows)
 Death (most extreme)
 No longer willing to take part
 No longer available
 Geographical move
 Negatively impacted by the treatment condition (e.g. anger, apathy, fr
ustration)
When the subjects select the experimenter
“
Good idea to plan for about 10% more session
s that you actually need
“
When the experimenter selects
the subjects
When the experimenter selects the subjects
“
In many experiments, the task is not recruiting participants but
selecting them.
Queries allow conditions to be placed on participant profile dat
a, participation history, and other participant-related data collec
ted by the system and it can also be combine with a sub-queri
es combined by AND OR statement or bracket.
“
When the experimenter selects the subjects
 It is always best to use people you do not know
 Do not only recruit people who seem friendly, and approach
able
 Control for this possible threat by constructing procedure ra
ndomly
 You must plan on your procedure for acquiring subjects car
efully
“
“
Things to avoid when selecting subjects
Some folklore about the
subjects
Some folklore about the subjects
In the folklore of psychologists, there is the notion that
sometimes, perhaps more often than we would expect,
subjects contacted early in an experiment behave differently
from the subjects contacted later.
(Resenthal)
“
“
Some folklore about the subjects
“
The first can be controlled, somewhat if you become highly pra
cticed before you run any subjects; the second is more difficult
to counteract.
“
Make sure that your random assignment procedure ensures th
at one condition is not finished up earlier than another, or you c
ould become an instrumentation threat.
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