Problem Words: Accuracy, Precision, and Reproducibility

The words accuracy, precision, and reproducibility are often misunderstood. Consider the following example and definitions:

Accuracy

Accuracy is the degree of conformity of a measurement relative to the known or true value of the quantity measured. Accurate means errorless or exact.

The accuracy of our in silico prediction of the protein’s 3-dimensional structure was assessed relative to the experimentally determined structure in the PDB database.

The accuracy of the experimentally determined structure relative to the protein’s true structure can not be determined.

Precision

Precision is, broadly speaking, the degree of refinement with which a measurement is made or reported. Precise means to conform strictly to rule or proper form.

Here we report a high precision X-ray structure of bacteriorhodopsin determined at 1.55 resolution.

Reproducible

Reproducible means that something can be copied or repeated with the same results.

Although the experimental methods described by Williams et al. (2008) were reproducible, we did not reproduce several key features of their protein structure.