ABSTRACT
The challenge of good measurement is to minimize the error. In fact, the most accurate measurements in the world simply keep the error very, very small. Error in the measurement of lactic acid can occur in any number of places. Lactic acid is expressed as a concentration, so any error in volume measurement of the blood will cause an error in the measurement of lactic acid concentration. If the free-throw test is actually a valid measurement of free-throw ability, we would expect the error to be reasonably small and the score to reflect the shooter's true free-throw ability. In the field of physical activity, a common factor that causes reliability errors is fatigue. If a teacher had her students run three miles and timed them, then had them repeat the run immediately, the results would show very poor reliability, for obvious reasons.
