Reliability

• internal reliability


  the extent to which a test or measure is consistent within itself. For example, the use of a standardised instructions and procedure for all participants.
• external reliability


  the extent to which a test produces consistent results over several occasions.
• issues with internal reliability

  -operationalisation of variables (precisely defining (IV) and measuring (DV) variables to create standardisation)-order/practice effects *-lack of standardisation of procedures-accuracy of the measuring tool
• order/practice effects


  -only relevant to repeated measure designs, where participants complete both conditions-whilst doing so, the participant can become practiced or better at the task the second time round because they are more familiar with the task, or they can underperform due to other factors, such as boredom
• counterbalancing


  This involves splitting the population or sample into halves; the first half complete condition one followed by condition two, the second half complete condition two followed by condition one. This in effect negates the impact of order/practice effects and increases internal reliability.
• standardisation


  -when procedures are not standardised it means that the way the research is conducted with each participant can vary.-this is an issue of internal reliability because the test is no longer consistent within itself. If you aren't giving everyone an identical experience you cannot be certain that the IV is leading to the change in the DV.
• standardisation (2)


  -standardisation (the process of ensuring the experience of the research is identical for everyone) involves providing a standard set of instructions that are read by the participant, using the same environment, and controlling as many aspects of the study as possible (which is easier to do in laboratory environments).-by standardising the procedures, the psychologist can attempt to establish cause and effect through reliable data collection.
• External reliability


  Consistency of results over time and across different populations
• assessing reliability


  there are three ways to assess reliability:split-half reliability (testing)test-retest reliabilityinter-rater reliability
• Internal reliability

  Higher internal reliability leads to higher external reliability
• Procedures and measures


  • The more controlled, the easier to replicate and the more likely to get similar results
  • Location of research can be a barrier to external reliability
  • Tests conducted in the field are subject to a wider range of uncontrolled variables (extraneous variables) and thus are less externally reliable
• split-half reliability testing


  -this involves splitting the test answers from a participant in half and seeing whether the individual got the same or similar scores on the two halves.-if so, internal reliability is high; if not, it is low and individual questions would need to be redesigned to ensure all questions were consistently testing the aims of the study.
• Conducting research in more controlled conditions

  Increases external reliability but decreases validity
• test-retest reliability


  -involves testing and retesting the same participants over time with the same test and comparing their scores-if the scores are the same, the test has external reliability
• inter-rater reliability


  -where two or more psychologists produce consistent results by using a standardised procedure, an agreed coding system or a correlation of their data.-this prevents variation of data collection by multiple psychologists or researchers