Research Methods/Measurement, Reliability, Validity
Research methods often depend on taking measurements, the validity of those measurements and the reliability of the global procedure. At first glance all this elements seems to be referring to the same, but you need to understand that all deal with the consistency in obtaining consistent and valid data at each level of complexity of he process.
Reliability is the degree of consistency of the examiner or the tools used to obtain the measurements.
Consistency deals with duplicability and the enforcement of the scientific method. All things being equal the results should remain the same.
Internal Consistency (reliability)Edit
Covers the degree of similitude in results regarding operations, inside a specific and limited range, regarding the locality of said operations.