Reliability

What is reliability in psychology?

Reliability refers to the consistency of a measure. In research, it means whether a study produces the same results when repeated (replicable).

What is internal reliability?

Internal reliability assesses the consistency of results across items within a test, ensuring all parts measure the same thing.

How is internal reliability assessed?

Using the split-half method, which measures the extent to which all parts of a test contribute equally to what is being measured by dividing the test into two halves and correlating the results.

What is external reliability?

External reliability refers to the extent to which a measure is consistent over time or across different situations (i.e. varies from one use to another).

What is inter-rater reliability?

The extent to which two or more observers record behaviour in the same way. It is assessed by comparing their results and checking for correlation.

How can inter-rater reliability be improved?

• Training observers

• Practice in a pilot study

• Better operationalisation of behaviour

• Ensuring all observers have equal ability to observe participants

What is test-retest reliability?

A measure of consistency over time where the same participants complete the same test on two different occasions, and results are correlated.

What does poor test-retest reliability indicate and what should be done?

• Indicates low consistency in the measure

• The test or task should be modified until a higher correlation is achieved