Selecting Research Partipants
First: who is your population of interest
Next: How do you get a sample:
- A representative sample of sufficient sample size is important external validity
Manipulating the independent variable
- construct an operational definition then
- develop a set of instructions/stimulation you can manipulate as the inedepdent variable
Strength of the Manipulation
0 in general, you want to make your manipulation as strong as possible maximizing the IV difference between the control and experimental groups
- however, you still want to make the manipulation
- realistic, for the sake of external validity
- ethical, to avoid harm to participants
MEASURING THE DEPENDENT VARIABLE: TYPES OF MEASURES
- pyssiological measures-
- behaviorial measures
- self report measures
Self report measures
- attitudes, opinions, emotional states, ect
Behavioral measures
whether or not a participant does something, how many times, reaction times, duration ect.
physiological measures
recording body measures (heart rate, hormone secretions, GSR, EMG, EEG, MRI, fMRI, ect.)
Measuring the Dependent variable: More considerations
- multiple measures
- sensitivity of the dependent variable
- you want your DV measure to be able to detect differences between the group
Measuring The Depdentent Variable: More Considerations
- multiple measures
- sensitivity of the dependent variable
- you want your DV measure to be able to detect differences between the group
- when measuring performance watch out for:
a. the telling effect: if the test is too easy, almost everyone gets 100%
b. floor effect: if the test is too hard, almost everyone fails
c. either way, you didn’t capture the full range of outcomes
Straightforward manipulations
Straightforward manipulation is a research method that involves presenting written, verbal, or visual material to participants
2 reasons for staged manipulation
- Researcher is trying to evoke a psychological state in the participants
- Simulating some situation that occurs in the real world
Confederate
an actor who who appears to be part of the experiment but is actually part of the manipulation
- used in staged manipulation
Solution to expectancy prob
- well trained researchers
- run all conditions simultaneously (however only achievable n certain circumstances)
- double blind
Final Planning Considerations
- research proposal:
includes literature review on background 4 study - pilot studies: small trail run of a study, figures out if experiment is plausible, and if changes need to be made
- manipulation checks
- does manipulation have in tended effect? Does Iv have intended effect
- debriefing
Describe the difference between a straight forward staged manipulation, using examples
Straightforward manipulation: manipulate variables with instructions and stimulus presentations
Staged manipulations
- stage events to manipulate IV succesfully
- can be used to create some sort of psychological state or simulate a real situation
What is a confederate? Why are they used in psychological research?
A confederate to be another participant in an experiment but is actually part of the manipulation
They can be useful when creating particular social situations
Discuss the overall dilemma regarding the strength of the independent variable manipulation. Why would you want to make the manipulation as strong as possible?
- a strong manipulation maximizes the differences between two groups and increases the chances that the independent variable will have a statistically significant effect on the dependent variable.
- In general, you want to make your manipulation as strong as possible, maximizing the IV difference between the control and experimental groups.
- This is how you figure out in the early stages of research if a relationship between the IV and DV exists at all. If it does, you can try more subtle differences to pinpoint what’s going on.
- However, you still want to make the manipulation:
- Realistic, for the sake of external validity, and
- Ethical, to avoid harm to participants.
Describe and give examples of self report behavioral and psychological measures of dependent variables
Self report used to measure attitudes, liking for someone, judgements, intended behaviors, emotional states ECT.
- having the participant rate how guilty a person was in an incident
Behahavioral: direct observations of behaviors
- rate, reaction time, duration, type of behavior
Physiological: recordings of responses of the body
Explain what is meant by a ceiling or floor effect measuring the dependent variable. Describe an example of a study that might produce a ceiling effect. Give another example for the floor effect
Ceiling effect- IV has no effect on DV only because participants reach maximum performance level
Floor: opposite of ceiling
tasks to easy that anyone can do it regardless of IV (ceiling)
tasks so hard no one can do it regardless of IV (floor)
What are demand characteristics and how can they be avoided? For example
1.Why is deception used in some studies
2. What is a placebo and what is it for?
DEMAND CHARACTERISTICS: any feature in an experiment that might inform participants of the purpose of the study. if participants know/figure out the purpose of the study, they may try to “help” confirm it.
- can be avoided by trying to disguise the dependent variable by using unobstructive measures or by placing FILLER ITEMS in questionnaires. one can also ask the participants about their perception of the purpose of the research.
- may be eliminated when people are not aware that an experiment is taking place or that their behavior is being observed.
- If the experiment involves a treatment, a placebo group (placebo = fake treatment) can be added to rule out patient expectations for improvement being the cause of improvement.
Explain how a double-blind experiment reduces expectancy effects
A double blind experiment ensures that the participants nor the experimenters knew which group has the placebo or treatment
- reduces expectancy effects because no one knows anything so no one can expect anything
What’s the purpose of a manipulation check
A manipulation check is used to directly measure whether the independent variable manipulation has the intendedd effect on the participants
