ERRORS How low can you go?. Errors in measurements… … are not called mistakes! … are not due to carelessness! … are always present! … can never be eliminated,

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Presentation transcript:

ERRORS How low can you go?

Errors in measurements… … are not called mistakes! … are not due to carelessness! … are always present! … can never be eliminated, but can and must be minimized!

CLASSIFYING ERRORS Errors can be classified according to SOURCE, TYPE and AMOUNT. The source of the error is where the error comes from. It is “who” is responsible for that specific error. Types of errors: gross, systematic or random. The amount of error is a measure of how much the error is, usually by a calculation.

SOURCE TYPE INSTRUMENTALGROSS HUMANSYSTEMATIC ENVIRONMENTALRANDOM ERRORS AMOUNT SINGLE MEASUREMENT ABSOLUTE RELATIVE PERCENT RELATIVE PERCENT DIFFERENCE

SOURCES of ERRORS HUMAN: due to experimenter. SYSTEMATIC: due to wrongly marked/faulty equipment. ENVIRONMENTAL: due to small fluctuations in the environment(al conditions).

TYPES of ERRORS DESCRIPTION GROSS: an error so big, it stands out. SYSTEMATIC: it has a pattern; always affect data in one direction (for more or less) RANDOM: no pattern; small errors due to uncontrollable conditions EXAMPLES Missing units; switching units, digits, instruments, or dimensions; missing whole “meter/yard”(s) Zero offsets; parallax Small fluctuations in the spread of data (for measurements of an object)

AMOUNTS of ERROR SINGLE MEASUREMENT: The error in a single measurement equals the precision of the instrument used to make it. ABSOLUTE, RELATIVE, PERCENT RELATIVE and PERCENT DIFFERENCE are all calculations. ABSOLUTE and RELATIVE have units. PERCENT RELATIVE and PERCENT DIFFERENCE are adimensional.

THE END © Lilian Wehner