Accuracy and precision, although used interchangeably in the English language, are very different in scientific terms. Accuracy is the closeness of a number of trials to the quantity’s actual value. Precision is the repeated measurements that show similar results. "A measurement system can be accurate but not precise, precise but not accurate, neither or both."¹ A measurement system is valid in a scientific setting if the results are both accurate and precise. Accuracy and precision can be numerically found by the following equations.
accuracy= (Number of true positives+number of true negatives)/(number of true positives+false positives+false negatives+true negatives )
precision= (number of true positives)/(number of true positives+false positives )
Where true and false positives and true and false negatives are denoted by binary classification test.
1. "Encyclopedia of Psychometrics." Retrieved from http://www.scribd.com/doc/136968050/Encyclopedia-of-Psychometrics