experimental designs

• Independent groups 

  All participants only experience one level of the IV, two separate groups experience two different conditions then performance is compared 
• Strengths of independent groups 

  -order effects aren't a problem 

  -participants less likely to guess the aims 
• Weaknesses of independent groups 

  -groups aren't the same in terms of participant variables which can act as confounding variables and reduce validity of findings (use random allocation to deal with this)

  -more time and mone spent on recruiting participants 
• Repeated measures 

  All participants experience both conditions of the experiment 
• Strengths of repeated measures 

  -participant variables are controlled so higher validity 

  -fewer participants so less time spent recruiting them 
• Weaknesses of repeated measures 

  -order of tasks may be significant, attempt to balance out order effects use counter balancing (ABBA)

  -repeating tasks an cause boredom or fatigue so order is confounding variable 

  -more likely participants will guess aim of study so possibility of demand characteristics 
• Matched pairs 

  Participants paired together on a variable relevant to experiment e.g. IQ in an attempt to control the confounding variable of participant variables 
• Strengths of matched pairs 

  -only take part in one condition so order effects and demand characteristics are less of a problem 
• Weaknesses of matched pairs 

  -participants can never be matched exactly so participant variables still exist 

  -time consuming and expensive especially if a pre test is required