experiemental designs

• independent groups design: participants are randomly assigned to one of two conditions, one condition is the experimental condition and the other is the control condition
• advantages of independent group studies:

  • no order effects = ppts only tested once so dont become fatigued
  • will not guess aim = higher realism
• independent groups disadvantages:

  • ppt variables = ppts are different in group acting as ev which reduces validity
  • less economical = need as twice as many ppts = more time spent recruiting which is expensive
• repeated measures design: same participant takes part in both conditions (experimental & control)
• repeated measures advantages:

  • ppts variables reduced = same person in both conditions has same characteristics
  • fewer ppt = less time spent recruiting them
• matched pairs design: participants matched on relevant variable then put into either experimental or control condition
• repeated measures disadvantages:

  • order effects can occur = may do worse/better completing same task reducing validity
  • ppts guess aims = change behaviour
• matched pairs advantages:

  • ppt variables reduced = ppt matched on variable linked to experiment enhancing validity
  • no order effects = only tested once so little fatigue
• matched pairs disadvantages:

  • matching is time-consuming and cannot control all variables so some ppts variables may occur
  • more ppts = more time spent recruiting