Scientific measurements are often repeated several times to increase confidence in the result. We can distinguish between two different kinds of certainty-called accuracy and precision-associated with such measurements. Accuracy refers to how close the measured value is to the actual value. Precision refers to how close a series of measurements are to one another or how reproducible they are. A series of measurements can be precise (close to one another in value and reproducibility) but not accurate (not close to the true value)