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Lecture 9

PSYB01H3 Lecture Notes - Lecture 9: Cortisol, Think Aloud Protocol, Construct Validity


Department
Psychology
Course Code
PSYB01H3
Professor
Connie Boudens
Lecture
9

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Chapter 9
Selecting Research Participants:
Most research projects involve sampling research participants from a population of interest
Ex. May want to study bipolar patients or all Canadians living in Canada
May be drawn from any population using probability (ex. Random) sampling or non-probability sampling
techniques
When it is important to accurately describe the pop. must use probability sampling
Probability sampling is crucial when conducting scientific polls
Most research interested in testing hypothesis about behaviour
In this case, focus of study is the relationships b/w the variables being studied and testing predictions
derived from theories of behaviour
Participants may be found in the easiest way possible using non-probability sampling (convinence or
haphazard)
Non-probability problem = difficulty to generalize results
^ but there is evidence that we can generalize to other populations and situations
Increasing sample size increases the likelihood that you will find an effect
b/c larger samples provide more accurate estimates of population values
Manipulating the independent Variable:
to manipulate I.V have to create an operational definition
must turn a conceptual variable into a set of operations – specific instructions, events and stimuli to be
presented to the research participants
I.V & D.V must be introduced within the context of the total experimental setting
all efforts must be made to control as many elements of the situation as possible to ensure internal validity
Setting the stage:
Planning the experience from the participants viewpoint
Have to do 2 things:
1) Provide the participants with the informed consent information needed for your study
2) Explain to participants why the experiment is being conducted
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Sometimes rationale given is completely true only rarely will you tell participants the actual hypothesis
oEx. Saying that you are conducting an experiment on memory when u are actually looking at a specific
aspect of memory
oIf participant know what you are actually studying they may try to look good by behaving in the most
socially acceptable way
oIf deception is necessary you have an ethical obligation to address the deception when you debrief the
participants at the conclusion of the experiment
No clear rule for setting the stage – the setting just must seem plausible to the participants
How the variable is manipulated depends on the variable, the cost, practicality and ethics of the procedure being
considered & researcher creativity
Types of Manipulations:
Straightforward manipulation
operationally define independent variables using instructions and stimulus presentations
oAbility to manipulate a variable simiply with written, verbal or visual material to the participants
oStimuli can be presented verbally, in written form, via videotape or with a computer
Ex. Study – impact of gendered language in job advertisement on job appeal
oMale & female participants
oOne condition used masculine words (dominant) other used feminine (caring)
o^ straightforward manipulation b/c the researchers just simply presented participants with stimulus
material (the advertisement) vs. creating an elaborate situation
Many operational definitions of I.V in all areas of behavioural research involve straightforward manipulation
Mundane realism: high level of this is, when the task involved in a study mimic experiences and conditions
present in everyday life
oEx. Juding how appealing an ad is something everyone does, but trying to forgot info and then
remember it not much ppl do so its low mundane realism
Staged Manipulations (a.k.a event manipulation)
Sometimes important to stage events that occur during the experiment in order to successfully manipulate the
I.V
Most frequently used b/c:
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1) The researcher may be trying to create some psychological state in participants (anger, frustration or
lowering self-esteem)
2) Needed to fake some situation that occurs in the real world
Ex. Study - effect on conversing with passenger on driving errors
oOne condition ppl drove alone – other condition drove with a passenger
oPresence of passenger didn’t affect how much time ppl spent looking @ the road but did reduce
participants ability to actually notice & respond to road hazards (pedestrians, motorcycles) especially for
ppl who were attracted to the passenger
o^ situation similar to what happens in the real world when ppl drive
Frequently employ a confederate (a.k.a accomplice) – appear to be another participant in an experiment but is
actually part of the manipulation
oUseful in creating a specific social situation
oEx. Ash line experiment
oCan be used in field experiments and lab research
Demands ingenuity and acting aibility
oUsed to involve the participants in an ongoing social situation, which they see as a real experience
Experimental realism: when a study engages and involves participants in a deep way (^)
Easier to have high experimental realism in staged vs. straightforward manip.
PROBLEM: allows for a great deal of subtle interpersonal communications that is hard to put into words, making
it difficult for other researchers to replicate the experiment
Complex manipulation is hard to interpret  if a lot of things happen during the experiment then what is
responsible for the results?
oEasier to interpret results when manipulation is straightforward
Strength of the manipulation:
The simplest experimental design has 2 levels of the independent variable
Manipulation strength considered by researcher when creating operational definitions
Stronger the manipulation = the better  means making the I.V maximally different while keeping everything
else b/w the two groups the same
Strong manipulation will increase chances that your results will reveal an effect of the independent variable on
the D.V – if one exists
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find more resources at oneclass.com
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