The advantage is that every question is checked for reliability. The disadvantages of the test-retest method are that it takes a long time for results to be obtained, and if too long an interval has been used then the participant may have changed in themselves which may mean a test is declared unreliable when it is in fact reliable. If the results from both presentations of the test significantly positively correlate then it is a reliable test.

The test-retest method involves administering an entire test to a participant, waiting for them to ‘forget’ the questions (which could take several months), and then readministering the test.

However it can only be effective with large questionnaires in which all questions measure the behaviour being researched.

Using the split-half method means the same participant can be used without having to wait for them to ‘forget’ the questions between the two halves of the test, and it is therefore a quick and easy way to establish reliability. If there is a significant positive correlation between the two halves then the questions are reliable. The split-half method involves randomly choosing half the questions on the test and comparing the results with the other half.They can be assessed for reliability using the split-half or test-retest methods, and if unreliable the questions can be improved until reliability is established. Psychological tests, such as self report questionnaires, need to be reliable.

For example, “aggressive behaviour” is subjective and not operationalised, but “pushing” is objective and operationalised.Īssessing and improving reliability of psychology tests

This means that the behaviour being observed can only be that behaviour. Ensuring behaviour categories are correctly and objectively operationalised.Training observers in the observation techniques being used and making sure everyone agrees with them.Where observer scores do not significantly correlate then reliability can be improved by: Observer reliability can therefore be assessed by correlating the data provided by the observers. If different observers provide significantly different observations of the same behaviour, then the data provided by those observers is unreliable. Of course, the exact same results will not be obtained each time as participants and situations vary, but a strong positive correlation between the results of the same test will indicate reliability.Īssessing and improving reliability of observersĪn observational research study using more than one observer needs to be assessed for reliability. In order to be able to class a test or research method as reliable, it must yield consistent results each time it is used. Reliability refers to the extent to which the measurement of a particular behaviour is consistent. It is important that psychology research can easily be repeated and yield the same results each time. Reliability and validity in psychology research

Reliability definition psychology