Accuracy and Precision
Accuracy and Precision : Accuracy is the extent to which a measurement reflects the true value. It is the tendency of test measurement to center around the true value. "Precise" means sharply defined or measured. Data can be very precise, but inaccurate. It would be precise but inaccurate to say that a meter equals 29.3748 inches. It would actually be more accurate to say that a meter equals a little over one yard, although that may not sound as impressive. An accurate measurement is one that is very close to the true value of the phenomenon we are observing. A precise measurement is one that has very little scatter: Repeat measurements give more or less the same value. If the measured data have high precision but poor accuracy, one may suspect that a systematic bias has been introduced, e.g., we are using an instrument where the zero position has not been set properly. If we do not know the expected value of a phenomenon but are trying to determine just that, it is obviously better to have accurate observations with poor precision than very precise, but inaccurate values, since the former will give a correct, but imprecise estimate while the latter will give a wrong, but very precise result. Acute Condition: A type of illness or injury that ordinarily lasts less than 3 months, was first noticed less than 3 months before the reference data of the interview, and was serious enough to have had an impact on behavior. (Pregnancy is also considered to be an acute condition despite lasting longer than 3 months). Age Adjustment, Direct Method: The application of age-specific rates in a population of interest to a standardized age distribution in order to eliminate differences in observed rates that result from age differences in population composition. This adjustment is usually done when comparing two or more populations at one point in time or one population at two or more points in time
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