experimental error Flashcards
True or False: Data of unknown quality are useless
true
True or False: It is necessary to determine the magnitude
of the accuracy and reliability in your
measurements
true
True or False: Not all laboratory measurements contain
experimental error.
false
Rule for buret measurements
all the certain figures and the first
uncertain figure!
Addition and Subtraction sigfigs
the smallest number of digits
to the right of the decimal sets the significance
Products and Quotients sigfigs
the smallest number of
significant digits determines significance
Logarithms sigfigs
keep as many digits to the right of
the decimal as there are significant figures in the original
number
Antilogarithms sigfigs
keep as many digits to the right of
the decimal as there are significant figures in the original
number
Instrument errors
failure to calibrate,
degradation of parts in the instrument, power
fluctuations,
Method errors
errors due to no ideal physical
or chemical behavior - completeness and speed
of reaction, interfering side reactions, sampling problems
Personal errors
occur where measurements
require judgment, result from prejudice, color
acuity problems
Constant errors
error is of the same
magnitude, regardless of the size of the
measurement. Examples: Solubility loss in
gravimetric analysis, reading a buret
Proportional errors
Es increases or
decreases with increasing or decreasing
sample size, respectively. In other words,
the relative error remains constant. Typically
a contaminant or interference in the sample
Random Errors
caused by uncontrollable variables which
normally cannot be defined
* The accumulated effect causes replicate
measurements to fluctuate randomly around the
mean
Gross errors
cause an experimental value to be
discarded
Lead to outlier’s and require statistical
techniques to be rejected
