Post on 26-Dec-2015
MEASUREMENT LIMITATIONS
• 1) ACCURACY–HOW CLOSE THE MEASUREMENT
IS TO AN ACTUAL OR ACCEPTED VALUE–DEPENDS ON YOU –GETS BETTER WITH PRACTICE
• 2) PRECISION–AGREEMENT OF A SET OF VALUES –REPRODUCIBILITY OF DATA–MEASUREMENTS CAN ONLY BE
AS PRECISE AS YOUR MEASURING TOOL (BASED ON HOW GRADUATED IT IS)
SIGNIFICANT FIGURES (DIGITS)
• INDICATES PRECISION OF AN INDICATES PRECISION OF AN INSTRUMENT INSTRUMENT • DEFINITION: ALL CERTAIN VALUES ALL CERTAIN VALUES
(FROM GRADUATIONS ON TOOL) AND ONE ESTIMATED OR AND ONE ESTIMATED OR UNCERTAIN VALUEUNCERTAIN VALUE (SPACE BETWEEN LAST GRADUATIONS)
RULES OF SIGNIFICANT DIGITS
• 1)ALL NONZERO DIGITS ARE SIGNIFICANT–EX: 275.68 g = 5 SIG FIGS
• 2) ZEROES BETWEEN 2 NONZERO DIGITS ARE SIGNIFICANT–EX: 1205 mL = 4 SIG FIGS
• 3) ALL ZEROES AFTER THE LAST NON-ZERO DIGIT IN A NUMBER WITH AN UNDERSTOOD DECIMAL ARE NOT SIGNIFICANT. (THEY ARE PLACEHOLDERS)–EX: 104 000 m = 3 SIG FIGS*THE NUMBER HAS BEEN
ROUNDED
• IF YOU WANT TO MAKE ZEROES SIGNIFICANT IN A NUMBER WITH AN UNDERSTOOD DECIMAL, PLACE A LINE OVER THE LAST ZERO THAT IS SIGNIFICANT.–EX: 104 000 m = 5 SIG FIGS
• 4) ALL ZEROES IN FRONT OF THE 1ST NON-ZERO DIGIT IN A NUMBER LESS THAN 1 ARE NOT SIGNIFICANT. (THEY ARE PLACEHOLDERS)–EX: 0.00589 g = 3 SIG. FIGS*THINK OF THESE NUMBERS AS
FRACTIONS; ONLY SIG FIGS GO IN THE NUMERATOR
• 5) ALL ZEROES AFTER A DECIMAL AND AFTER THE 1ST NON-ZERO DIGIT ARE SIGNIFICANT–EX: 0.07050 L = 4 SIG FIGS 30.00 mg = 4 SIG FIGS*BE CAREFUL BECAUSE YOUR
CALCULATOR REMOVES THE ZEROES AT THE END OF NUMBERS