WAP Glossary

Question 1

Validity

Answer 1

A measurement is valid if it measures what it is supposed to be measuring.

Question 2

True value

Answer 2

The value obtained in an ideal measurement (with the exception of a fundamental constant where the true value is considered unknowable)

Question 3

Accuracy

Answer 3

The closeness of agreement between a measured value and the true value. (Random and systematic affect it.)

Question 4

Precision

Answer 4

The closeness of agreement between values obtained by repeated measurement. (Affected by random only.)

Question 5

Repeatability

Answer 5

The precision obtained when measurement results are obtained by the same person/group repeating a single method over a short timescale.

Question 6

Reproducibility

Answer 6

The precision obtained when measurements are obtained by different people using different pieces of apparatus.

Question 7

Uncertainty

Answer 7

The interval in which the true value can be considered to lie with a given level of confidence or probability.

Question 8

Error

Answer 8

The difference between a measurement and the true value, if one is thought to exist (source of uncertainty).

Question 9

Resolution

Answer 9

The smallest measuring interval of an instrument (source of uncertainty).

Question 10

Significant figures

Answer 10

The number of digits following the first non-zero digit. Depends on the resolution of instruments, and should usually eventually be rounded to the same SF as the lowest resolution.