Defining Repeatability
Repeatability in scientific measurement refers to the closeness of agreement between successive measurements of the same quantity, carried out under the same conditions of measurement. These identical conditions include the same measurement procedure, same observer, same measuring instrument used under the same conditions, same location, and repetition over a short period of time.
Key Principles for Achieving Repeatability
To achieve high repeatability, all variables other than the quantity being measured must be kept as constant as possible. This means using the exact same equipment calibrated identically, ensuring the same environmental conditions (temperature, humidity), and having the same person perform the measurements consistently. Any variation under these 'same-condition' tests indicates a lack of repeatability within the measurement process itself.
Practical Example of Repeatability
Imagine a scientist measuring the mass of a single chemical sample five times using the same digital balance, in the same lab, at the same temperature, and within a few minutes. If the readings are 10.02g, 10.01g, 10.02g, 10.00g, and 10.02g, these results show high repeatability because they are very close to each other, indicating minimal variation when conditions are kept consistent.
Importance in Science and Engineering
Repeatability is fundamental for establishing confidence in measurement results. High repeatability is a prerequisite for precision, assuring that an experiment or test can consistently produce similar results under controlled conditions. This consistency is vital for validating experimental procedures, comparing data, and ensuring that any observed differences are due to actual changes in the phenomenon being studied, rather than inconsistencies in measurement.