NECESSITY FOR CHECKING ERRORS.--Dr. Stratton says,--"No measurements, whether they be psychic or physical, are exact beyond a certain point, and the art of using them consists largely in checks and counter checks, and in knowing how far the measurement is reliable and where the doubtful zone begins."[18] Capt. Metcalfe says,--"Errors of observation may be divided into two general classes; the instrumental and those due to the personal bias of the observer; the former referring to the standard itself, and the latter to the application of the standard and the record of the measurement."[19] The concrete illustration given above is an example of careful checking up. Under Scientific Management so many, and such careful records are kept that detecting errors becomes part of the daily routine. SUMMARY RESULTS OF MEASUREMENT TO THE WORK.--Under Traditional Management, even the crudest measurement of output and cost usually resulted in an increase in output. But there was no accuracy of measurement of individual efficiency, nor was there provision made to conserve results and make them permanently useful. Under Transitory Management and measurement of individual output, output increased and rewards for the higher output kept up the standard. UNDER SCIENTIFIC MANAGEMENT BETTER METHODS AND BETTER WORK RESULTS.--Under Scientific Measurement, measurement of the work itself determines 1. what kind of workers are needed. 2. how many workers are needed. 3. how best to use them. Motion Study and Time Study measurement,-- 1. divide the work into units. 2. measure each unit. 3. study the variables, or elements, one at a time. 4. furnish resulting timed elements to the synthesizer of methods of least waste. ACCURATE MEASURING DEVICES PREVENT BREAKDOWNS AND ACCIDENTS.--The accurate measuring devices which accomplish measurement under Scientific Management prevent breakdowns and accidents to life and limb. For example.-- 1. The maintained tension on a belt bears a close relation to its delay periods. 2. The speed of a buzz planer determines its liability to shoot out pieces of wood to the injury of its operator, or to injure bystanders. Scientific Management, by determining and standardizing methods and equipment both, provides for uninterrupted output. EFFECT ON THE WORKER.--Under Traditional Management there is not enough accurate measurement done to make its effect on the worker of much value. Under Transitory Management, as soon as individual outputs are measured, the worker takes more interest in his work, and endeavors to increase his output. Under Scientific Management measurement of the worker tells 1. what the workers are capable of doing. 2. what function it will be best to assign them to and to cultivate in them.