Control and Pilot Studies

• Control


  control is one of the key features of science. It is necessary to have tight control of extraneous variables to establish a cause-and-effect relationship (to say for certain that the independent variable is directly impacting the dependent variable)
• Random allocation

  this is placing participants in the different conditions of the independent variables in a fair and unbiased way to reduce researcher bias and increase the validity of the research
• Random allocation process

  -assign each participant a number

  -use a random number generator to pick out one number at a time to place in each group

  -continue until each condition is full

  -match the numbers with the participant
• Counterbalancing

  Some investigations will use the same participants in each condition (repeated measures design)

  • a problem with this is participants may perform worse in condition B due to tiredness/boredom ('fatigue effect'), or they may perform better due to practice ('practice effect'). These are collectively known as 'order effects' as they are caused by the order in which particpants complete conditions
  • to control order effects you can counterbalance (the 'ABBA method')
• Counterbalancing process

  -half of the participants take part in condition A and then complete condition B

  -the other half of the participants take part in condition B and then complete condition A
• Purpose of counterbalancing

  -it is to control the impact of order effects (practice, fatigue or boredom)

  -it allows order effects to be distributed evenly across both conditions

  -this makes each condition of the IV occur as the first task and the second task equally

  Counterbalancing doesn't eliminate order effects which will be present because there are two seperate tasks to be completed by each person. Half will do better/worse in Condition A and half will do better/worse in Condition B
• Randomisation

  randomisation refers to the use of chance whenever possible to reduce the influence of the researcher on the design of the investigation

  this is an attempt to control investigator effects and therefore increase the validity of the research
• Randomisation process

  -when choosing words for a memory test, collect a list of 100 words from a database (randomly select)

  -assign each word a number

  -enter all numbers into a random number generator

  -use the random number generator to select the required number of words

  -match the selected numbers with the words

  this will ensure the order of the words in the list is due to chance and not how the researcher decides to order them. This avoids the researcher having an influence (they might group certain words together that are similar which may affect the DV - memory recall)
• Standardisation

  this means ways in which procedures/materials/instructions within an investigation are kept the same for all participants
• Standardisation process

  -use standardised instructions that are the same for all participants - these are clear written instructions about exactly what they need to do in the experiment

  -ensure participants are given the same ethical information (e.g a copy of the same consent form/debrief)

  -use the same materials for each participant (words lists, videos etc)

  -use the same environment to conduct the study in

  -conduct the study at the same time of day
• Demand characteristics

  this is when participants may change their behaviour because they know they are taking part in a study. They may try and work out the aim of the experiment and as a result their behaviour may alter

  this lowers the validity of the research findings as participants are not acting naturally and therefore the researcher is not measuring the genuine behaviour of the participants
• Types of demand characteristics

  -social desirability bias - this is where participants at differently to appear more desirable

  -'please you' effect - when participants change their behaviour to try and please the experimenter

  -'screw you' effect - where particiapnts change their behaviour to try and disrupt the experiment
• Reducing demand characteristics

  -deceive the participants about the true aim of the experiment

  -not telling the participants that they are being observed/conducting a study in the real world

  -not telling participants which condition of the independent variable they are taking part in
• Investigator effects

  this is when the presence of the investigator may influence the behaviour of the participants or their influence on the design of the study may influence the findings of the study

  for example, the investigator may unknowingly suggest to the particpants how they are expected to behave (they way they ask questions/respond, smiling at them)

  • this lowers the validity of the findings because the researcher cannot be confident that they are measuring what they intent to measure, which is the genuine natural behaviour of the participants
• Reducing investigator effects

  -use standardised instructions that are the same for all participants

  -reduce interaction with participants as much as possible so you cant consciously/unconsciously influence them (use non-participant observation)

  -use random sampling to ensure the sample is selected fairly

  -use random allocation to ensure that the investigator isn't choosing which participant is in each group
• Pilot studies

  this is a small-scale trial run of the investigation that happens before the full study. This will involve a smaller number of participants to check the procedure and materials

  this will ensure that if there are issues with the procedure of a study or the materials used then these can be checked to ensure they are appropriate and effective. If not they can be corrected before the main study

  This will help the researcher avoid wasting time and money
• What the researcher should check for in a pilot study

  • the task isn't too easy (ceiling effect)
  • the task isn't too difficult (floor effect)
  • the equipment works (TV, computer, video camera)
  • the participants understand the instructions
  • an observational study has camera positioned correctly
  • an observational study has clear behavioural categories that are easy to understand and use

  pilot studies are not used to check the results, they are just used to check the method