Topic 2 IV Flashcards
What is in independent variable?
- The experimental factor (s) that distinguish groups
- Manipulated by the experimenter
What is a manipulated variable?
A factor directly manipulated by experimenter e.g. whether participant gets drug A, B, C
What is a subject variable?
A factor NOT directly manipulated by experimenter e.g gender or where they live
If the IV is manipulated what experiment will it be?
A TRUE experiment
causal
Under a True experiment what can be found out?
- Prediction
2. Explanation
If the IV is Subject what experiment will it be?
A QUASI experiment
correlation
Under a Subject experiment what can be found out?
- Prediction
NOT EXPLANATION
If IV (X) observes result Y what are the four possible explanations for this?
- X causes Y
- Y causes X
- 3rd Factors Z causes X and Y
- Chance
Explain X causes Y
Difference between IV levels is directly responsible for difference between the groups on the DV
Explain Y causes X
Observed difference on DV is determining what level of the IV participants are in e.g. elderly with responsibility vs health
Explain 3rd factor causes both X and Y
A third factor determines which level of the IV participants are in , and also determining observed differences between groups on the DV
e. g. smoking (IV) and hearth disease (DV , Y/N)
- stress is the third factor
- Can cause people to smoke
- Can cause heart disease
What is a control group? And how is it different from the experimental group?
- The comparison group (baseline)
2. Differs from experimental groups by absence of experimental treatment
What is the placebo effect?
- The group believes they are receiving the treatment but are not. Start to feel ‘effects of the treatment’
- Performance in group gives estimate of size of placebo effect
What is the effect of incorrectly choosing levels of the independent variable?
Obscures the effect of the Independent variable
What is a Single-Blind Study?
Used when dealing with placebo / experimental intervention groups where the participant must not know which group they are in
What is a Double-Blind Study?
Neither participant nor experimenter knows the condition that the participant is assigned to
What are Demand Characteristics?
Cues in a situation that people interpret as ‘demands’ for a particular behaviour
- Participants bring attitudes that influence behaviour
- Environment and experimenter can contribute
Describe a between subjects experiment
Each participant is tested in only one IV level
-subject variables in between-subjects design may act as confounds
Describe matching
A way to control subject variables which may have acted as confounds
Impactful variables are matched in treatment conditions e.g. same amount of variable in each group
What is error variance?
It’s that we vary in response without being influenced by variables e.g. you can’t hit the keyboard at exactly the same time each time therefore gives variation
What decreases due to error variance?
The likelihood of detecting actual difference between levels of the Independent variables
What is the participant condition for Within-subjects design?
Each subject is tested in every level of the IV
In a within subjects design what does each participant serve to themselves as?
As his or her own control for confounding
What is a problem with within-subjects design?
Order Effect = order in which participants experience levels can cause confounding
Practice Effect = participants’ results could be impacted by repeating a task (can be postive of negative)
What technique protects against order effects?
Counterbalance
Explain counterbalancing
Each treatment condition is equally exposed to practice effects and demand characteristics
e.g. 1/2 participants are tested deprived -> rested
1/2 participants tested rested -> deprived
What is a control variable?
Any extraneous variables that are held constant during experiment
What can uncontrolled variables become?
Confounding variables
What three things are important to control in a study?
- Participants/ subject variables
- Demand characteristics
- Experimental materials
