Week 3 PSyb01h3 2012-09-27
Basic Issues and Concepts
-------------------Variables: their types and purpose in research Measurement issues
Definition: something that varies! Something that could take on different values.
o Feature of a person, situation, etc, that can take on one value or more.
Examples: level of creativity, numbers of siblings, height, room temperature, color of food.
o Main purpose of research is to simplify the complex by explaining variability.
Variability in behaviour
o Differences in the way people behave in response to the same stimulus
systematic (explained): explainable variability
o Ex: a mouse runs through the classroom..
What could I do? I may be shocked. But other ppl may react differently, like creaming, or
some ppl may be calm.
Psychology is trying to know why ppl behaving in certain way. Particular stimulus affect ppl
in different way.
What matters here?
Gender? Women is more sensitive, men are likely to take charge the situation
City Vs. country person? Urban ppl more scared; country ppl is more calmed?
Animal lovers? Maybe someone is more tolerated
Color of mouse? Black mouse is more scary?
Still some variation in responses left between ppl ----this is random----for now…
o Variables must have 2+ values or levels
o Value: number representing one of many possible “states” of the variable
Example: some possible values of height are 6’, or 4’2”
o Score: a specific value for a given person
Example: my score on the variable of height is 5’7”
Independent vs. dependent variables
o Independent variable: I.V
manipulated by researcher –
assumed to be cause
o Dependent variable:
outcome of experiment
measurable and it is measured
Assumed to be caused by i.v.
o the D.V. Depends on the IV. And I.V causes the D.V.
What’s the i.v? What’s the d.v?
o There will be a difference between the number of boys and the number of girls pushing and shoving
in the playground
D.V. pushing and shoving o 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 room
I.V.: level of noise in the room;
Two values: quiet and noisy
D.V: number of words recalled depend on the noise level in the room
o 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. Mental disorder
Two values; serious mental disorder VS. anybody else
DV. medication taken
o Students who sit further forward in class will achieve a higher grade in the final examination
I.V: where you sit in class; level is not identified
D.V. grade in the course
o First-step: determining whether variable is categorical or continuous.
Categorical (taxonic, qualitative, nominal):
Values are discrete, qualitatively different categories
Measured on nominal scale
o Biological sex is always considered as nominal variables
Nominal means in name only.
Some categorical variables are nominal variables
o Like gender, political parties
Continuous: you could have different values on a certain variables
Values differ in degree from each other
Measured on ordinal, ratio, or interval scale
Determines how you can analyze data
Example: you want to figure out the relationship between age and phone book use
to serve for a yellow page printing company
o You ask ppl in different ways to see if they have phone books
o You got two categories: age under or above 25 yrs old; two groups of ppl
Scales of measurement
o Scales of Measurement: Ordinal
Ordered or ranked data
Intervals may or may not be equal
Ex: finishing place in race
It does not mean the difference the different place are equal
It is just a ranking data
They reason you have to figure what kind of data is measured is for the statistical
purpose. Actually, the ranking data is hard to be statistic . o Scales of Measurement: Interval
Ordering, but with equal intervals
The "zero point" is arbitrary, and values can be negative
Everything is relative; zero is meaningful
o Scales of Measurement: Ratio
Same as interval, but with a true zero point (i.e. 0 quite literally means none)
Money in your wallet
Time to finish race
Scales of Measurement Summary
o Operational definition: clearly Procedures for measuring or manipulating the variable
It is related to how you will measure the variables
o Specific enough to allow replication—that someone would be able to do your study without contact
Straightforward for concrete variables, more challenging for abstract ones.
You have to make decision how you will measure your variablesa key decision
Operational definitions – let’s try some...
o Examples: - You may have different ways to measure the stress of a person; like # of negative life
- The way you choose to study will affect you research
- For example, you want to do the physiological patterns Vs stress
o You may need to face the person, and you may need many machines to measure
o Which may make you research very expensive
o Then your research may not be replicable
- There is no perfect way but may be better way of worse way in doing pa