Reliabilioty

Reliabilioty

1. Types of reliability

   • Test-retest: Apply the same test at different times, under the same standardised conditions and to the same people. Results should be consistent to show reliability. The coefficient of stability is consistency over time.
   • Parallel or alternate form reliability: Similar results should be obtained with a parallel (similar) test. The coefficient of equivalence is similar measures.
   • Internal consistency: Correlate different parts of the measure to one another, e.g. split the measure in half and calculate the correlation of the results – this is the coefficient of internal consistency. The Spearman-Brown formula is used to correct the underestimation of the true correlation between the various parts of the test because they are based on fewer items than the complete test is based on. The coefficient of internal consistency is Cronbach alpha/Kuder Richardson.