Psych 231 Research Methods in Psychology Class Experiment Class Experiment Print out the Class experiment listed on syllabus page exercise and bring it to labs this week Turn in your data sheets pass to front ID: 638133
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Slide1
Experiment Basics: Variables
Psych 231: Research Methods in PsychologySlide2
Class ExperimentClass Experiment
Print
out the
Class experiment
(listed
on syllabus page)
exercise and
bring it to labs this week
Turn in your data sheets (pass to front)
I will analyze the data and the results will be discussed in labs this week
Turn in your consent
forms
Quiz 5 (chapter 4) is due FridaySlide3
Exam 1
Mean:
77.9%
Median:
79%
Range: 57-93
Results
If you want to go over your exam set up a time to see me Slide4
Exam 1
Common errors:
Four Cannons of scientific method (& pg 7-10 of the textbook)Slide5
Exam 1
Common errors:
A researcher examined the relationship between music and mood. He presented two groups of participants the same video clips but the two groups received different musical soundtracks. Following the presentation of the videos, participants completed a questionnaire designed to measure their current mood.
Identify the Research Design used in the study
Identify a major advantage of using this research design for this study
Identify a major disadvantage/limitation of using this research design for this study.
Experiment: manipulated the music (IV) and measured
the effects on mood (DV). Major advantage: ability to make causal claimsMajor disadvantage: (several possible answers, generalizability)Slide6
So you want to do an experiment?
What behavior you want to examine
Identified what things (
variables
) you think affects that behavior
You’
ve got your theory. Slide7
So you want to do an experiment?
You
’
ve got your theory.
Next you need to derive predictions from the theory. These should be stated as hypotheses.
In terms of conceptual variables or constructsConceptual variables are abstract theoretical entities
Consider our class experiment
Theory & Hypotheses:
What you try to
recognize
&
how connected to your social network you feel.
Social vs
.
Non-social websites
Cell phone presenceSlide8
So you want to do an experiment?
You
’
ve got your theory.
Next you need to derive predictions from the theory.
Now you need to design the experiment.
You need to operationalize your variables in terms of how they will be:ManipulatedMeasured
ControlledBe aware of the underlying assumptions connecting your constructs to your operational variablesBe prepared to justify all of your choicesSlide9
Constants vs. Variables
Characteristics of the psychological situations
Constants:
have the same value for all individuals in the situation
Variables
: have potentially different values for each individual in the situation
Variables in our experiment:
Connectedness to social network Type of website Recognition memory performance Time for unscrambling
Kind of
cell phone present
…Slide10
Variables
Conceptual vs. Operational
Conceptual variables
(constructs) are abstract theoretical entities
Operational variables
are defined in terms within the experiment. They are concrete so that they can be measured or manipulated
Conceptual
Social connectednessSocial concepts/wordsRecognition Memory
Operational
Cell phon
e presence or absence
Websites social or non-social
Word scramble testSlide11
Many kinds of Variables
Independent variables (explanatory)
Dependent variables (response)
Extraneous variables
Control variables
Random variables Confound variables
Correlational
designs have similar functionsSlide12
Many kinds of Variables
Independent variables (explanatory)
Dependent variables (response)
Extraneous variables
Control variables
Random variables Confound variablesSlide13
Independent Variables
The variables that are manipulated by the experimenter (sometimes called
factors
)
Each IV must have at least
two levelsRemember the point of an experiment is comparison
Combination of all the levels of all of the IVs results in the different conditions in an experimentSlide14
Independent Variables
1 factor, 2 levels
Condition 1
Condition 2
Factor A
1 factor, 3 levels
2 factors, 2 x 3 levels
Cond 1Factor ACond 3
Cond 2
Cond
1
Factor B
Cond
3
Cond
2
Factor A
Cond
4
Cond
6
Cond
5Slide15
Manipulating your independent variable
Methods of manipulation
Straightforward
Stimulus manipulation
- different conditions use different stimuli
Instructional manipulation – different groups are given different instructions
StagedEvent manipulation – manipulate characteristics of the context, setting, etc.Subject (Participant)
– there are (pre-existing mostly) differences between the subjects in the different conditions leads to a quasi-experiment
Presence or absence of cell phone
Social vs
.
non-social websitesSlide16
Choosing your independent variable
Choosing the right levels of your independent variable
Review the literature
Do a pilot experiment
Consider the costs, your resources, your limitations
Be realisticPick levels found in the “real world”
Pay attention to the range of the levelsPick a large enough range to show the effectAim for the middle of the rangeSlide17
Identifying potential problems
These are things that you want to try to avoid by careful selection of the levels of your IV
(may be issues for your DV as well).
Demand characteristics
Experimenter bias
Reactivity
Floor and ceiling effects (range effects)Slide18
Demand characteristics
Characteristics of the study that may give away the purpose of the experiment
May influence how the participants behave in the study
Examples:
Experiment title:
The effects of horror movies on moodObvious manipulation: Having participants see lists of words and pictures and then later testing to see if pictures or words are remembered betterBiased or leading questions:
Don’t you think it’s bad to murder unborn children?Slide19
Experimenter Bias
Experimenter bias
(expectancy effects)
The experimenter may influence the results (intentionally and unintentionally)
E.g.,
Clever Hans One solution is to keep the experimenter (as well as the participants) “blind
” as to what conditions are being testedSlide20
Knowing that you are being measured
Just being in an experimental setting, people don
’
t always respond the way that they
“
normally” would. Cooperative
DefensiveNon-cooperative
ReactivitySlide21
Floor effects
A value below which a response cannot be made
As a result the effects of your IV (if there are indeed any) can
’
t be seen.
Imagine a task that is so difficult, that none of your participants can do it. Slide22
Ceiling effects
When the dependent variable reaches a level that cannot be exceeded
So while there may be an effect of the IV, that effect can
’
t be seen because everybody has
“maxed out”Imagine a task that is so easy, that everybody scores a 100%
To avoid floor and ceiling effects
you want to pick levels of your IV that result in middle level performance in your DVSlide23
Range effects
Floor
: A value below which a response cannot be made
As a result the effects of your IV (if there are indeed any) can
’
t be seen.Imagine a task that is so difficult, that none of your participants can do it.
Ceiling
: When the dependent variable reaches a level that cannot be exceededSo while there may be an effect of the IV, that effect can’t be seen because everybody has “maxed out”Imagine a task that is so easy, that everybody scores a 100%
To avoid
floor
and
ceiling effects
you want to pick levels of your IV that result in middle level performance in your DV