Lecture 3 – Chapter 3 The Starting Point
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Transcript of Lecture 3 – Chapter 3 The Starting Point
Research TerminologyVariables
Variable: Any measurable aspect of behavior or influence on behavior that may change
Or…things you manipulate
and things you measure
Independent Variable: IV
Dependent Variable: DV
Independent Variable:
Normally (true experiment), it is the variable that you manipulate
ANY VARIABLE THAT DEFINES SEPARATE GROUPS
…”I” do the research…it’s what “I” manipulate
Either give some subjects 100mg of a drug or give them 25mg or placebo
Here the IV is DRUG (varying doses)
So, by randomly assigning them to a drug dose you are creating the groups (conditions) of the experiment
Sugar pill
IV
10 mg
1 mg
Either give some subjects 20, 60 or 40 watts and test their performance on a math test
60 watts20 watts 100 watts
Then vary the type of math test: algebra, geometry
Independent Variable: Normally (true experiment), it is the variable that
you manipulate…but in a quasi-experiment not really manipulated
the IV is the preexisting condition that the subjects brings into the experiment
(also called the “subject” or “classification” variable)
ex: sex, age, ethnicity
IV: Levels
In general, the number of levels of an independent variable is the number of experimental conditions
Dependent Variable:
In either True experiment, Quasi-experiment, or Correlational research:
The variable that you hypothesize to have a relationship with the IV..that you expect to be affected by the IV
The variable that you measure
The response of your subject
Naturalistic Observation – Low constraint
The observation of subjects in their natural environmentThe researcher imposes no limits or changes in the environment or behavior of the subjects
No manipulation
No IV
DV? Behavior?
“Variable of interest”
Case Study – Low constraint
The subject is in a moderately limiting environmentThe researcher intervenes only slightlyAn in-depth description of one subject, organization or event
ex: medical field: Case of H.M.
No manipulation
No IVDV? Behavior?
“Variable of interest”
Correlational research – Constraint
Quantify the degree of relationship between two variableMeasurement procedure must be carefully defined and precisely followedNo manipulation of variables – two sets of measurements in the same subject then correlate
0 10 20 30 40 50 60 70 80 901000
10
20
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percentage (class grade)
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IV? Grouping variable DV? response
Experimental Research – highest constraint“True Experiment”
ex: want to investigate the effects of a drug on depression
This should be easy now!IV? Grouping variable
DV? response
One last Variable – Not a good thing
Extraneous VariableExtraneous: coming from outside,
foreign, not permanent, irrelevant
Any variable or factor not controlled for by the experimenter that might affect the DV
Threat to validity of experimentInternal Validity: are we testing what we set out to
test?Methodological soundness of experiment
testing subjects on a memory test …temperature in the room is HOT …impact on
the tests results
Examining the effects of alcoholon driving and obeying posted signs…but you don’t assess their vision
examples of extraneous variables
Experimental Research – highest constraint“True Experiment”
Control: Systematic methods
reduce threats to validity
Extraneous variables (confounds)
without bias assign Subs to groups RANDOM ASSIGNMENT the setting is ALL about control
measurement procedures carefully designed and precisely followed
Research Ethics
Human Subjects Institutional Review Board (HSIRB)
- Consists of members of community & peers- Review research proposals – Yea or Nay- Assure that project meets ethical standards (set by APA. NIH & institution)
Informed Consent: a form that provides the subject with enough info to make an “informed” decision