Variables

• Operationalising variables

  Clearly describing the variables (IV and DV) in terms of how they will be manipulated (IV) or measured (DV)
• Independent variable


  The variable that the experimenter manipulates (changes)
• Dependent variable


  The variable that is measured to tell you the outcome
• Extraneous variable


  Variables that if not controlled may affect the DV and provide a false impression that an IV has produced changes when it hasn’t
• Confounding variable

  An extraneous variable that varies systematically with the IV so we cannot be sure of the true source of the change to the DV
• covariables are the variables investigated in a correlation that are compared to see if they have an association
• Control of Extraneous variable

  1. Order effects can occur in a repeated measures design and refers to how the positioning of tasks influences the outcome e.g. practice effect or boredom effect on second task

  2. Participant variables- participants in one group may differ in a significant way from participants in another group

  3. Situational variables- factors in the environment that may affect the DV

  4. Investigator effects- These result from the effects of a researcher’s behaviour and characteristics on an investigation

  5. Demand characteristics- Occur when participants try to make sense of the research situation they are in and try to guess the purpose of the research or try to present themselves in a good way
• Control of Order effects

  Can be controlled using counterbalancing (A way of trying to control for order effects in a repeated measures design, e.g. half the participants do condition A followed by B and the other half do B followed by A)
• Control of Participant variables

  This risk can be reduced via random allocation (participants randomly assigned to groups) or by matched pairs
• Control of Situational variables

  These can be reduced by using a standard procedure
• Control of Investigator effects

  Can be controlled using double blind control (participants are not told the true purpose of the research and the experimenter is also blind to at least some aspects of the research design) or standardised instructions and/or procedure (see lab experiments)
• Control of Demand characteristics

  Can be reduced using Double blind control or Single blind control (Participants are not told the true purpose of the research)