Measurement terms and calculations

Question 1

Precision

Answer 1

Describes how close measurements are when taken under the same conditions.

Question 2

Accuracy

Answer 2

Measures how close an individual test result is to the accepted reference value.

Question 3

Uncertainty

Answer 3

The range of measurement values in which the reference value lies and is expressed as a range.

% uncertainty= maximum uncertainty/volume of glassware x 100

Question 4

Titration tables

Answer 4

Titre = final burette reading - initial burette reading

Mean titre = calculated using the tires which are within 0.1cm^3 of each other.

Trial titre should NOT be used.

Question 5

Anomaly/outlier

Answer 5

A value in the set of results which does not fall within the inherent variation.

Question 6

Confidence

Answer 6

A qualitative judgement indicating the extent to which a conclusion is justified by the quality of the evidence.

Question 7

Repeatability

Answer 7

The precision of measurement results over a SHORT TIMESCALE by the same people using the same equipment in the same place.

Question 8

Reproducibility

Answer 8

The precision of measurement results over a WIDER TIMESCALE by different people using the same equipment and the same environmental conditions.

Question 9

Resolution

Answer 9

The smallest change in a quantity being measured which can be detected by an instrument.

Question 10

Validity

Answer 10

A valid measurement , measures what it is supposed to.

A valid investigative procedure, answers the question being asked.

The absence of a negative control reduces validity.