Laboratory test 1 Revision notes

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  • Created by: shauna
  • Created on: 09-12-12 18:28


  • 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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Experiment Types

True Experiment 

  • 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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Experimental Design

Independent Groups

  • random allocation of pp's to seperate conditions
  • Avoids order effects
  • Increased effects of individual differences

Repeated Measures

  • pp's perform under both conditions
  • Eliminates individual differences
  • Increaes order effetcs

Matched Pair's

  • 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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Face Validity

  • Does it measure what it claims to measure

Criterion related Validity

  • What it measures corresponds to some independent measure of the same thing.

Predictive Validity

  • Score on this predicts a score on somethig else (E.g SATS good predictive validity in predicting performance in college).

Construct Validity

  • tool measures psychological concept it claims to measure
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