experimental designs

• what is an independent group design? 


  this uses 2 separate groups, one group of participants only perform in one condition of the experiment.
• what is positive about an independent group design? 


  it avoids order effects, as participants only take part in one condition of the experiment.
• what is positive about an independent group design? 


  it reduces demand characteristics, as participants only take part in one condition of the experiment, this increases the validity.
• what is negative about an independent group design? 


  participant variables may affect the results as one condition may have all females, for example, which could affect the results.
• what is negative about an independent group design? 


  more participants are required to take part in the different conditions of the experiment, this is more costly.
• what is repeated measures? 


  the same participants are used in the same conditions, so you are comparing the same people
• what is positive about repeated measures? 


  fewer participants are required, this makes the design less costly and more time-consuming.
• what is positive about repeated measures? 


  the use of the same participants across the conditions reduces the possibility of participant variables
• what is negative about repeated measures? 


  order effects can occur as participants take part in both conditions of the experiment
• what is negative about repeated measures? 


  demand characteristics are more likely to occur as participants are more likely to guess the aim of the experiment when they take part in both conditions.
• what is matched pairs? 


  participants are matched in terms of participant variables such as age or IQ. they are paired up with someone who is the same or similar to them. after matching takes place, the participants are treated much like those in an independent group
• what is positive about matched pairs? 


  it avoids order effects, as participants only take part in one condition of the experiment
• what is positive about matched pairs? 


  demand characteristics are less likely
• what is positive about matched pairs? 


  it reduces participant variables as it ensures that each condition has a variety of abilities and characteristics
• what is negative about matched pairs? 


  it is very difficult, if not impossible, trying to find close or exactly matched pairs, this means that individual differences may still play a role.
• what is negative about matched pairs? 


  more participants are required as different people take part in the different conditions of the experiment, this is more costly.
• what is random allocation? 


  each participant has an equal chance of being assigned to one group or another
• what is the procedure of random allocation? 


  1. write down all (total-22) of the participants names and put them into a hat
  2. pick out a name and allocate the participant to condition 1 (water). pick out another name and allocate the participant to condition 2 (energy drink)
  3. repeat this until there are an equal amount of participants (11) in each condition
• what is counter-balancing? 


  this is used to reduce order effects
• what is the procedure for counter-balancing?


  1. split into 2 equal groups of 11
  2. the 2nd half do the 2nd condition (energy drink) first then do the 1st condition (water) second
  3. the first half do the 1st condition (water) first then do the 2nd condition (energy drink) second