Experiments- Method, Control of Variables, Design, Types

Experiments- Method, Control of Variables, Design, Types

1. Method

   • Aims
     • General statement describing the purpose of the experiment
   • Hypotheses
     • Testable statement on the relationship between the variables
       • Based on theory
     • Directional
       • Clarifying the type of difference between the two conditions
         • Drinking energy drinks increases your talkativeness
       • Used when previous research suggests particular outcome
     • Non-directional
       • Stating that there will be a difference between the conditions, but not the type
         • Drinking energy drinks affects your talkativeness
       • Used when there is no previous research into the area
   • Variables
     • Independent Variable
       • Aspect of the experiment which is manipulated/changed
     • Dependent Variable
       • Measured the record effect of changing the IV
     • The hypothesis should state the IV and DV
       • E.g. The group who drink energy drinks will be more talkative than the group who drink water
         • IV= type of food
         • DV= IQ
     • Operationalisation
       • Making the variables measurable
         • E.g. the group who drink 200ml of energy drink will say more words in 10 minutes than the group who drink 200ml of water

2. Control of variables

   • Extraneous variables
     • Unwanted variables, other than the IV, which may influence the DV
     • E.g. gender, lighting in room, age
     • Don't vary systematically with the IV
   • Confounding variables
     • Unwanted variable, other than the IV, which may have influenced the DV
     • Unsure of true source of changes in DV
     • Vary systematically with the IV
     • E.g. personality
   • Demand characteristics
     • Guessing the aim of an experiment and reacting accordingly
     • Act in a way which they think is 'expected' or over-perform to please
     • Under-perform to sabotage results
     • Unnatural behaviour
   • Investigator effects
     • Researcher favouring certain participants
     • Unconscious clues
     • Selection of materials, participants, instructions etc.
     • Leading questions
   • Randomisation
     • Reduces effects of EV/CVs and investigator effects
       • Random generation
       • Order of conditions randomly determined
   • Standardisation
     • Same environment, instructions and experience

3. Experimental Design

   • Independent Groups
     • Two groups selected, one does control condition, other does experimental condition
     • Performance of two groups compared
   • Repeated Measures
     • One group selected, do both the control and the experimental condition
     • Performance in each condition compared
   • Matched Pairs
     • One group chosen, then another based on characteristics of participants in the first group. Carried out like IGD
     • Performance of two groups compared