Formulation of Testable Hypotheses (AQA GCSE Psychology): Revision Note

The alternative hypothesis

• A hypothesis is a precise, testable statement of the relationship between the variables being investigated

• The alternative hypothesis predicts that the independent variable (IV) will affect the dependent variable (DV)

  • It is the hypothesis of a difference between conditions

• The alternative hypothesis must include both the IV and the DV, and both must be operationalised, for example:

  • Operationalised IV = whether children observe an aggressive or a non-aggressive adult model

    Operationalised DV = the number of imitative acts of aggression the child performs

• A non-directional alternative hypothesis of difference for the above study on aggression could be written as:

  • There will be a difference in the number of imitative acts of aggression performed by children who observe an aggressive adult model and those who observe a non-aggressive adult model

• A hypothesis of difference can also be written directionally, predicting which condition will score higher, e.g:

  • Children who observe an aggressive adult model will perform more acts of imitative aggression than children who observe a non-aggressive adult model.

Hypotheses for correlational studies

• Correlational studies do not have an IV and a DV

  • Instead they measure two co-variables to see whether they are related

• The hypothesis therefore predicts a relationship (correlation), not a difference, and both co-variables must still be operationalised, for example:

  • There will be a relationship between the number of hours of sleep the night before a test and the number of marks scored on the test

• The matching null hypothesis (see below) predicts no relationship:

  • There will be no relationship between the number of hours of sleep the night before a test and the number of marks scored on the test

• A correlational hypothesis can also be directional, predicting the type of relationship: positive (both rise together) or negative (one rises as the other falls), e.g:

  • As hours of sleep increase, the number of marks scored on the test will increase

The null hypothesis

• Researchers must allow for the possibility that the IV has no effect on the DV, so a null hypothesis is written alongside the alternative hypothesis

  • The null hypothesis predicts no difference between conditions

• The null hypothesis must be the direct opposite of the alternative hypothesis: same conditions, same operationalised DV, for example:

  • A researcher predicts that loud music harms memorising:

    • Participants will recall fewer words from a list when loud music is playing than when memorising in silence

  • The matching null:

    • There will be no difference in the number of words recalled when memorising with loud music playing compared with memorising in silence

• Once the results are in:

  • If there is no difference between conditions, the null hypothesis is accepted

  • If there is a difference between conditions, the null hypothesis is rejected and the alternative hypothesis is accepted

• The null hypothesis for the study on aggression could be written as:

  • There will be no difference in the number of imitative acts of aggression performed by children who observe an aggressive adult model and those who observe a non-aggressive adult model