experimental designs

• explain the method of independent groups: 


  • seperate groups of participants for each level of the iv
  • there are usually two levels of the iv the control group and the experimental group
  • control group has no influence of the iv and is used as a comparison to the experimental group
• strengths and weaknesses of independent groups 


  strengths: order effects are not an issue because the participant only tries one condition reducing practice effects

  weaknesses: individual differences, each group has a different set of participants which posses diff skills and backgrounds so can affevt valid of results
• explain repeated measures 


  • all participants undergo all of the conditions of the experiment
  • results then of each of them are compared to see wether there is a difference in performance
  • all game part in all conditions
• what are the strengths and weaknesses of repeated measures 


  strengths: participant variables r removed as each participant undergoes each condition so is compared against themselves. ——fewer participants are needed so each produce two set of results

  weaknesses: order effects, participants get to practice tasks so if performance increases it may be becayse they practiced
• explain matched pairs 


  • participants only take part in one condition
  • they are split into two groups but are similar
  • they are tested on participant variables and matched up for comparison
  • the pairs undertake one of two conditions
• strengths and weaknesses of matched pairs 


  strengths: no order effects as they only undertake one condition

  participants are matched up so participant variables are moderately reduced when compared

  weaknesses: takes time and not always exact, not everyone is the same so method is a lot of effort for minimal gain
• what’s a quantitative method 


  use data that can be counted, usually given as numbers
• what’s a qualitative method 


  data expressed in words, and given meaning usually in a non numerical format
• what’s ecological validity 


  a type of external validity that refers to the extent to which the findings can be generalised to real life setting
• explain labatory experiments 


  aim to measure the effect which one or more independent variable has on a dependant variable
• strengths and weaknesses of a laboratory experiment

  strengths: extraneous variables can be controlled so allows confident conclusions

  standardised procedures allowinf for replication

  weaknesses: lacks ecological validity so not reflective of everyday activities

  increase in demand characteristics so participants are aware they are being studied and can change behaviour
• explain field experiments 


  • studies using experimental design that occurred in a natural setting
  • researchers examine how the manipulation of at least one iv changes in a dv in context of a natural environment
• strengths and weaknesses of field experiments 


  strengths: more realistic as they are conducted in a natural environment

  follow a standardised procedure to account extraneous variables

  weaknesses: lack of control over variables

  ethics, if they are unaware they are being studied there is no consent
• explain natural experiments 


  • studies using experimental design that occur in a natural setting
  • does not change the iv it changes naturally
• strengths and weaknesses of natural experiments 


  strengths: high validity they include real life changes in natural settings

  weaknesses: rare occurance so effects the iv being measured

  • unique characteristics researchers cannot allocate conditions which may lead to influence extraneous variables
• explain quasi experiments 


  a study that is almost an experiment but lacks manipulatoon of variables. the iv has not been determined by anyone
• strengths and weaknesses of a quasi experiment 


  strengths: carried out under controlled conditions

  weaknesses: cannot randomly allocate participants to conditions meaning confounding variables are present