TOLERANCES OF GRADUATED EQUIPMENT Tolerances are usually larger than ±1 in the last decimal place Tolerances are often provided by the manufacturer 5-mL Volumetric Pipet : ± 0.02 mL 50-mL Volumetric Buret : ± 0.03 mL 100-mL Volumetric Flask : ± 0.08 mL A tolerance in the hundredths place means the measurement should be given to the hundredths place Reading for a 5-mL Volumetric Pipet : 5.00 mL Expected range for the measured value : 4.98 mL to 5.02 mL 5.00 ± 0.02 mL EX2-1 (of 11)

READING GRADUATED EQUIPMENT For all measurements, the last digit recorded is an estimated digit EX2-2 (of 11)

Most Accurate Graduations: One Celsius Degree Estimated digit: Tenths Reading : 47.6 Cº EX2-3 (of 11)

Most Accurate Graduations: One-Tenth of a Milliliter Estimated digit: Hundredths Reading : 9.36 mL 1.41 mL EX2-4 (of 11)

Most Accurate Graduations: One Milliliter Estimated digit: Tenths Reading : 60.0 mL EX2-5 (of 11)

Most Accurate Graduations: One Celsius Degree Estimated digit: Tenths Reading : 42.0 Cº EX2-6 (of 11)

Most Accurate Graduations: One Milliliter Estimated digit: Tenths Reading : 81.5 mL EX2-7 (of 11)

Most Accurate Graduations: One-Tenth of a Milliliter Estimated digit: Hundredths Reading : 24.16 mL EX2-8 (of 11)

ACCURACY AND PRECISION ERROR – The difference between a measured value and the “true” value of a property ACCURACY – The agreement between a measured value and the “true” value Measured values close to the “true” value are ACCURATE EX2-9 (of 11)

ACCURACY AND PRECISION , but values are “accepted” if they are derived from repeated measurements (density of alcohol at 25°C: 0.7852 g/mL) It is rare to know the “true” value of property EX2-10 (of 11)

ACCURACY AND PRECISION PRECISION – The agreement among several measured values of the same quantity, and reflects the reproducibility of a given measurement Measured values close to the each other are PRECISE EX2-12 (of 11)