Practical vocabualry (bio, chem)

ACCURACY

A measurement result is considered accurate if it is judged to be close to the true value.

CALIBRATION

Marking a scale on a measuring instrument.

This involves establishing the relationship between indications of a measuring instrument and

standard or reference quantity values, which must be applied.

For example, placing a thermometer in melting ice to see whether it reads 0 °C, in order to check if

it has been calibrated correctly.

DATA

Information, either qualitative or quantitative, that has been collected.

ERRORS

See also uncertainties.

Measurement error

The difference between a measured value and the true value.

Anomalies

These are values in a set of results which are judged not to be part of the variat ion caused by

random uncertainty.

Random error

These cause readings to be spread about the true value, due to results varying in an unpredictable

way from one measurement to the next.

Random errors are present when any measurement is made, and cannot be corrected. The effect

of random errors can be reduced by making more measurements and calculating a new mean.

Systematic error

These cause readings to diff er from the true value by a consistent amount each time a

measurement is made.

Sources of systematic error can include the environment, methods of observation or instruments

used.

Systematic errors cannot be dealt with by simple repeats. If a systematic error is suspected, the

data collection should be repeated using a different technique or a different set of equipment, and

the results compared.