- IV ~ The variable manipulated by the experimenter
- IV Levels ~ two or more condions of expereiment
- DV ~ The variable measured (subject behaviour) by the expereimenter
- Systematic EV'S ~ Confounding variable with levels varying systematically
- Random extraneous variable ~ variable randomly distributed across experiment, thus unlikely to confound.
Controlling Confounding Variables
- Random Allocation to control person variables
- Counterbalancing to control for order effects
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- IV fully controlled by experimenter
- IV not fully controlled by expereimenter. No random allocation of pp's to conditions as orgnismic variables prevent this from being done
- examines relationship between two co-variables. One variable may be considered causual hence referred to as the predictor variable, other is the predicited variable.
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- random allocation of pp's to seperate conditions
- Avoids order effects
- Increased effects of individual differences
- pp's perform under both conditions
- Eliminates individual differences
- Increaes order effetcs
- similar to repeated measures EXCEPT pairs equated on variables seen as relevant to behaviour examined, one member assigned to one condition, next to other, randomly
- Difficult and time consuming
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Levels of Measurement
- categorical data (Chi-square)
- scores are ranked. E.g. 1st,2nd,3rd in race (MW, S, W)
- equal units of intervals between scores. No absolute Zero, E.g thermometer or finishing time of racers
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- Does it measure what it claims to measure
Criterion related Validity
- What it measures corresponds to some independent measure of the same thing.
- Score on this predicts a score on somethig else (E.g SATS good predictive validity in predicting performance in college).
- tool measures psychological concept it claims to measure
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