Practical skills - Glossary

Question 1

Calibration

Answer 1

Marking a scale on a measuring instrument.
This involves establishing the relationship between indications of a measuring instrument and standard or reference quality values, which must be applied.
For example placing melting ice on a thermometer and checking if it reads 0 degrees celsius to see if it properly calibrated.

Question 2

Data

Answer 2

Information, either qualitative or quantitive

Question 3

Measurement Error

Answer 3

The difference between a measured value and the true value

Question 4

Anomalies

Answer 4

These are values in a set of results which are judged not to be a part of the variation caused by random uncertainty

Question 5

Random Error

Answer 5

These cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurements 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.

Question 6

Systematic Error

Answer 6

These cause readings to differ from the true value by a consistent amount each time a measurement is made.
Sources of systematic error can include the environment, methods or observation.
Systematic errors cannot be dealt with by simple repeats. Instead a different technique or different set of equipment is needed and then the results compared.

Question 7

Evidence

Answer 7

Data that has been shown to be valid

Question 8

Zero Error

Answer 8

Any indication that a measuring system gives a false reading when the true value of a measured quantity is 0 e.g. the needle on an ammeter failing to return to 0 when no current is flowing.
This may indicate systematic uncertainty.

Question 9

Accuracy

Answer 9

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