Experimental method

• What is experimental method? 


  Involved the manipulation of an independent variable (IV) to measure the effect on the dependent variable (DV)
• What is an aim?


  A general statement of what the researcher intends to investigate, the purpose of the study.

  • The aim is the intended purpose of a psychological investigation
  • It outlines what the researcher is trying to discover
  • Often starts with the phrase 'To investigate'
• What is a hypotheses?

  A hypothesis is a statement that is made at the start of the study and clearly describes the relationship between variables as stated by the theory.

  • There are two main types of hypothesis:

  1. Alternative hypothesis
  2. Null hypothesis
• What is a directional hypothesis?

  A hypothesis where there is a clear difference anticipated between two groups. eg: higher/lower
• What is a non-directional hypothesis?

  A hypothesis that simply states that there is a difference but does NOT specify
• What is an independent variable?


  Some aspect of the experimental situation that is manipulated by the researcher- or changes naturally- so the effect on the DV can be measured
• What is a dependent variable?


  The variable that is measured by the researcher. Any effect on the DV should be caused by the change in the IV.
• What is an operationalisation variable?


  Clearly defining variables in terms of how they can be measured
• What are the four different types of experiment?

  1. Laboratory experiment
  2. Field experiment
  3. Natural experiment
  4. Quasi-experiment
• What is an alternative hypothesis?

  A statement which predicts a difference or correlation in results
• What is a null hypothesis?

  A statement which predicts no difference or correlation in results
• What are the two types of alternative hypothesis?

  1. directional alternative hypothesis
  2. non-directional hypothesis
• How do you write a hypothesis?

  How a hypothesis is written depends upon whether the researcher is conducting an experiment or a correlation
• Writing a hypothesis for an experiment:

  • In an experiment, the researcher is looking for a difference
  • When a researcher is writing a hypothesis for an experiment, they must include - an IV and a DV
  • They must also operationalise the Iv (by stating the conditions) and the DV
• What is written when a researcher has a good idea of the experiment's outcome?

  Directional hypothesis
• What does a directional hypothesis indicate?

  The researcher predicts a specific outcome
• What should a researcher write if they are unsure of the experiment's outcome?

  Non-directional alternative hypothesis
• How does a non-directional alternative hypothesis begin?

  With the phrase "there will be a difference"
• How do directional and non-directional hypotheses differ in terms of researcher certainty?

  Directional indicates certainty; non-directional indicates uncertainty
• Writing a null hypothesis for an experiment:

  • The null hypothesis for an experiment will always start with the phrase "there will be no difference..."
  • For example: "there will be no difference in the number of words found between the ppts who are in silence and the ppts who listen to music"
• What is a confounding variable?

  Uncontrolled extraneous variables that affect the DV and therefore confuse the results