Variable, Aims and Hypothesis

• Independent variable:

  • a factor that is directly manipulated by the experimenter to observe the effect of this on the dependent variable.
• There are at least two levels of the IV (groups/conditions).
• Dependent variable:


  • the variable that is measured by the experimenter.
• What is operationalising?

  • Operationalization means turning abstract concepts into measurable observations. E.g. what the levels of IV are or how we are going to measure the DV.
• Extraneous variable:

  • it is any other variable other than the IV that might have a potential affect on the DV - therefore producing invalid results.
• Extraneous variables can include both participant and situational variables.
• Participant variable:

  • Characteristics of the participants - age, intelligence etc. which may have an affect on DV.
• Situational variable:

  • features of the environment - distracting noise, time of day etc. which may impact the DV.
• Research aim:

  • a general statement about the purpose of the study and what it intends to find out from the research.
  • its will be phrased like - 'to investigate whether'
• Hypothesis:

  • it is a statement predicting the outcome of a piece of research.
• 2 Types oh hypothesis:

  • alternative hypothesis - includes one-tailed (directional) and two-tailed (non-directional) hypothesis.
  • null hypothesis
• Alternative hypothesis:

  • predicts a difference or a correlation. Predicts the IV does have a significant effect on the DV.
  • e.g. 'there will be a significant difference...'
• Null hypothesis:

  • predicts no difference or correlation. Predicts IV has no effect on DV.
  • e.g. 'there will be no significant difference...'
• Rules of writing a hypothesis:

  1. statement about the predicted relationship - identify both the IV and DV.
  2. include all levels of the IV.
  3. IV and DV in the hypothesis must be operationalised.
• One-tailed (directional) hypothesis:

  • states the expected direction of the difference.
• Two-tailed (non-directional) hypothesis:

  • does not state the expected direction of difference.
• Rough formula for writing hypothesis:

  • null - 'there will be no significant difference in the [DV] of [IV condition 1] compared to [IV condition 2]'.
  • two-tailed - 'there will be a significant difference in the [DV] of [IV condition 1] compared to [IV condition 2]'.
  • one-tailed - 'participants who [IV condition 1] will [DV] more/less than participants who [IV condition 2].'