Reliability is the extent to which a measurement instrument, test, or research procedure consistently provides the same or very similar results each time it is used under the same conditions, indicating the stability and dependability of the measurement. A reliable measure is one that is free from significant random error, meaning that the scores or observations obtained are consistent and not due to chance variations in the measurement process. In social science research, reliability is a crucial aspect of the quality of data, as it ensures that the findings are consistent and can be trusted. Different methods are used to assess reliability, such as test-retest reliability (consistency over time), internal consistency (consistency across items within a measure), and inter-rater reliability (consistency across different researchers using the measure).