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Lecture 3

PSYB01H3 Lecture Notes - Lecture 3: Dependent And Independent Variables, Categorical Variable, Mental Disorder

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Connie Boudens

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Lecture 3
Basic Issues and Concepts
Slide 2: Variables
Definition: something that varies something that can take on different values
Feature of a person, situation, etc, that can take on one value or more.
Examples: number of siblings, level of creativity, colour of food at room temperature
Main purpose of research is to simplify the complex by explaining variability look at key
variables that can explain the differences in behaviour
In psychology try to figure out which variables account for most of the differences in the
way that organisms responds to a particular situation
Slide 3: Variability in Behaviour
Differences in the way people (or other organisms) behave in response to the same stimulus
We want to figure out what causes the differences in the way people react to the same stimulus
All variability in behaviour can be classified into two types: systematic & random
Systematic variability can be explained, random variability cannot be explained
Ex: a mouse runs through the classroom
What happens?
o Some people may jump, scream, be surprised, get very upset, some won’t care
o Research in psychology tries to look at why people behave in different ways helps us
predict behaviour, explain different types of behaviour, and why variability exists
o Don’t really care about stimulus that have the same effect on people
o Variables that may affect how people react to the mouse:
gender women are usually conditioned to jump & scream, men socialized to
be tough and expected to take care of the mouse situation
where you grew up; urban vs. rural rural people may be less affected by it as
their used to animals , urban residents may associate it with rats which means
plague and infestation & potential for some sort of virus
people who have pets vs. those who don’t – those who have pets may be more
tolerate to mice and less scared
colour of the mouse might also be a variable for example, black mouse might
cause more fear
o try to figure out which variables causes differences in how people react to a mouse
running across the room
find the variables that cause individual differences in the way people react to injections, prepare
for surgery, write exams all important questions to ask

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Lecture 3
with these questions try to figure out why some people are different from others on a particular
in theory you should be able to find everything that causes different behaviour amongst people
at this point we don’t have the technology to figure out all variables; in the future may be able
to use brain imaging technology and research methods related to neurology to find all variables
that cause a difference
at this point we can figure out some systematic variables ( explained) but will still have some
random variables ( unexplained)
Slide 4:
Variables must have 2 or more values or levels or else it doesn’t vary (therefore not a variable)
Value: number representing one of many possible “states” of the variable
Example: some possible values of height are 6’, or 4’2
Score: a specific value for a given person for a particular variable
Example: my score on the variable of height is 5’7”
Example: my score on the variable eye colour is brown
**Slide 5: Independent vs. Dependent Variables
Independent variable (IV): manipulated by researcher assumed to be cause (usually assumed to be the
cause of behaviour) can be measured (if it’s not an experiment) & manipulated (experiment)
Dependent variable (outcome variable): outcome of experiment assumed to be caused by
independent variable only measured, never manipulated
- Dependent variable caused by changes in the independent variable
- The value of the dependent variables depends on the value/level of the independent variable
Slide 6: What is the Independent Variable? What is the Dependent Variable?
There will be a difference between the number of boys and the number of girls pushing and
shoving in the playground
IV gender, DV pushing/shoving
There will be a difference between the number of words recalled by participants who have
learned them in a noisy room and participants who have learned the same words in a quiet
IV noise level (with 2 possible values quiet, noisy), DV memory (# of words

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Lecture 3
People who suffer with a serious mental disorder are more likely to take more medication than
people who do not suffer with a serious mental disorder.
IV severity of mental disorder, DV how much medication an individual takes
Students who sit further forward in class will achieve a higher grade in the final examination
IV seat chose in lecture , DV grade on final exam
Slide 7: Measuring Variables
First-step: determining whether variable is categorical or continuous.
Categorical ( AKA taxonic, qualitative, nominal):
Values are discrete (not overlapping), qualitatively different categories
Measured on nominal (in name only) scale
Ex categorical: biological sex, type of dwelling, political party affiliation
Values differ in degree from each other
Measured on ordinal, ratio, or interval scale
Ex continuous: age, working memory capacity, time it takes to complete puzzle, gender,
height, weight
Determines how you can analyse data
If you only measure two categorical variables such as if men and women differ in terms of how
much they support the progressive conservative party, liberal party, and NDP; very little you can
say from the numbers
In political study do large scale studies about variables that impact voting behaviour in the
states they only have two parties democrats & republic these are categorical & only two
values therefore can retrieve much information from it
With continuous variables there is many more values the variable can take on so you can get
more out of your research
Example you’re trying to figure out the relationship between age and whether people know
what a phone book is & its use
This can help with advertising what types of products/services should be advertised in
the yellow pages based on the people who use them
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