Precision describes the consistency among repeated results, whereas accuracy concerns how close a result is to the true or accepted value. A method can therefore produce tightly grouped measurements while still giving an inaccurate result. Chemists evaluate both properties separately so that reproducible data are not mistaken for correct data.
Instrument resolution, sample handling, and consistency in carrying out the procedure all affect the spread of repeated results. Random error also contributes to variation between measurements. Controlling these factors helps reduce unwanted differences and makes it easier to determine whether observed variability comes from the method, the equipment, or the handling of the sample.
These measures describe how widely repeated measurements differ from one another. The range compares the most separated results, while variance and standard deviation summarize variation across the data set. Smaller values indicate tighter agreement among measurements, allowing chemists to compare the consistency of analyses and identify procedures that produce greater variability.
Chemists perform repeated analyses under the same conditions, keeping the sample treatment, instrument use, and procedural steps as consistent as possible. They then examine the resulting spread with a range, variance, or standard deviation. This workflow reveals the method's repeatability and helps identify variability that may require procedural or equipment-related investigation.
When two analytical methods are applied repeatedly under comparable conditions, their variation can be evaluated using the same statistical measure. The method producing the smaller spread demonstrates greater precision for that comparison. Such evaluations support method selection and validation, particularly when consistent quantitative results are important for chemical analysis.
Precision helps chemists decide how many significant figures a result can reasonably support. Reporting more digits than the observed variation justifies can imply unwarranted reliability. Precision assessment also strengthens quality control by revealing inconsistent analyses, supporting reproducible research, and showing whether an experimental procedure performs consistently over repeated measurements.