week 6

• what do t-tests do?

  compare the means of the samples
• what do descriptive stats do?

  describe the qualities of the data, including measures of dispersion and central tendency
• what do inferential stats do?

  attempt to make generalisations based on the data
• when can we use t-tests

  when there is 1 DV and 1 IV
• what are the two types of t-tests

  • independent - data sets from two separate populations are studied
  • dependent - data from the same population at two different times is analysed
• the value of T is equal to the

  (observed - expected difference) / estimate of SEM between means
• what are the assumptions for t-tests generally

  • parametrics
  • data is normally distributed
  • data is continuous
• what are the assumptions specifically for an independent t test

  • data is independent
  • the variance is the same for both data sets
• what is randomisation 


  researchers try to leave as much of the study up to chance as possible to avoid bias, e.g. which group the ppts are put into
• evaluate a between-subjects design

  • avoid order effects
  • avoids demand characteristics
  • avoids fatigue effect
  • participant variables may threaten validity
  • require more participants
  • less time consuming
  • differential attrition may cause problems