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Lecture 7

PSYB01H3 Lecture Notes - Lecture 7: Intravenous Therapy, Repeated Measures Design, Methodological Advisor

Course Code
Connie Boudens

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Conducting Experiments
Decisions to be made
Who to use as participants and how many
Manipulation of the i.v.
Measuring the d.v.
Exact procedure
Controlling for expectancy effects
Manipulation checks? - checks to make sure you’re manipulation of the I.V. worked the
way you wanted it to
Example: if person on a stand (eye witness) makes contact with the jury how does it
affect the perception of how honest the person is?
o Forensic psychology looks at eye-witness research because people are really
interested if eye witnesses of a crime can be trust because sometimes that’s the
only evidence that the prosecution has
o Therefore massive amount of research on how credible eye witness research is
and how accurate the things are that eye witnesses reports
o Another big area is court room behaviour = what are the things people do in
court rooms that make them more or less credible
This example will be used through-out the lecture: does it matter if the eye-witness makes
contact with the jury?
How many?
o In general a bigger sample is better up to a certain point there is an upper limit
because when there is a lot of people even the smallest differences between
groups are going to seem like significant differences ( by product of having large
o If you’re going to conduct a study should always try to get as many participants as
you possibly can
o Participants can be hard to get even if it’s an online survey – therefore don’t
usually have to worry about getting too many participants
o Statistical consultant can help you figure out your upper limit of participants
o In general minimum amount of people in each group = 30 ppl/condition (cell)
don’t really know where this number came

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o So would have 30 people in the control and 30 different people in the experiment
= 60 participants
o In a 3x2 design - = 6 different conditions = total participants = 30 x 6 = 180
o When you have too many independent variables and different levels need a lot of
participants therefore wound up in a position doing a repeated measures design
Who? best choice is to use a random sample selected from the population of interest
But most of the time this is not what is done
o Convenience
Most psychology studies use this
Usually undergraduates at whatever university the study is being
conducted at
However online/internet allows for people from general public from
various backgrounds/ages/etc. are now used
o Snowball
You ask your friend to ask some of their friends and etc. etc.
It’s a really easy thing to do especially over e-mail can simply forward
the study
Used a lot of times in the early stages of research
o Internet-based
Good source of participants but less control over who is going to be
filling the surveys out
Can get a broader range of participants
Probability or non-probability sample? main question to ask is do you need a
probability sample or will you be okay with a non-probability sample
o If all other things are equal a probability sample will be better because data will
be more generalizable but this isn’t always the goal
o May need to get things done more quickly therefore might not always have time
to get a probability sample (very time consuming)
o Sometimes probability samples are not really necessary really depends on the
research questions and the resources that are available large organizations have
a lot of resources to be able to get a probability samples
Setting depends on how you’re going to conduct your study
o Computer lab space
o Lab with computers set up
o Mood and ability to make discriminations between two closely related concepts
can all be done on a computer
o Regular lab space
o Can be any type of space not necessarily a lab with testing equipment
o An office space can be a lab!

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o Enclosed space where you can control the type of stimuli participants are exposed
to & control the people that are coming and going
o Secure area where you can keep materials locked up and keep control of things
o AV equipped?
o Do you need audio visual equipment in your space?
o Or any other type of specialized type of equipped this will dictate what kind of
space you use for your experiment
o Some AV equipment you can pick up and move such as gaze-direction
equipment tracks where the person is looking on the computer screen and it
gives you an a lot of different types of output dots of where the person looks,
where the persons eyes move while looking at the image
o In advertising research they use gaze-direction equipment to see what people
focus on the most in the advertisement want participants to optimally focus on
the product
o Can also do this for commercials and different areas of commercial light up
depending on what participants looked at
o Other equipment is more immobile/large such as respiration equipment for
physiological measures or brain imaging (MRI, cat scans, etc.) more
problematic because time consuming, more money, and more no-shows if testing
is off-site
o More natural environment
o Quasi-experiment in the outdoors, lobby, etc.
o Such as Southerners/Northerner experiments utilized a hallway = used natural
environment and lab space
o Setting depends on what the research question is and what study involves settings
mentioned above = most common settings
o Eye-witness and contact they make with jury can have studies in many settings
o Ex. in computer setting have participants watch videos of trials(made-up) with
vary levels of the independent variable (eye contact) and have them make a
decision about how honest they thing the eye witness is - levels of I.V. vary from
no contact to always makes eyes
o Ex. with more money & resources can set up a court room setting and have
participants watch how whole thing works out but this is a lot more time
consuming and requires a lot more money participants can come in in groups as
long as they don’t talk to each other
Manipulating the IV doesn’t necessarily mean you’re changing the I.V variable during the
experiment just means you’re introducing different levels of the I.V.
o Straightforward
o Low realism
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