Particle size analysis in the pharmaceutical industry has long been a source of debate regarding how best to define measurement accuracy; the degree to which the result of a measurement or calculation conforms to the true value. Defining a 'true' value for the size of a particle can be challenging as the output of its measurement will differ due to variations in measurement approaches, instrumental differences and calculation methods. Consequently, for 'real' particles, a universal 'true' value does not exist and accuracy is therefore not a useful characteristic. Accordingly, precision is then a measure of the ability to reproducibly measure of value of unknown value. This paper proposes, in place of accuracy, a means to define the 'appropriateness' of a measurement in line with the Critical Quality Attributes (CQA) of the material being characterized. The decision as to whether the measurement is correct should involve a link to the CQAs; that is, correlation should be demonstrated, without which the measured particle size cannot be defined as a Critical Material Attribute (CMA). Correspondingly, methods should also be able to provide sufficient precision to demonstrate discrimination relating to variation in the CQA. The benefits and challenges of this approach are discussed.