Useful Terms (p.38 PSH)

Question 1

Define:

Accuracy

Precision

Answer 1

Accuracy

• The closeness of agreement between a test value and the truev value

Precision

• Unrelated to the true value
• It is the closeness of agreement between independant measurements under the same conditions
• It only depends on random errors

Question 2

Define

Anomaly

Error

Answer 2

Anomaly

• is a value in a set of results that is judged not to be part of the inherent variation

Error

• is the difference between an individual measurement and the true value (or accepted reference value) of the quantity being measured

Question 3

Define confidence

Answer 3

• is a qualitative judgement expressing the extent to which a conclusion is justified by the quality of the evidence

Question 4

Define

Repeatability

Reproducability

Answer 4

Repeatability

• Precision of results obtained by the same persons using the same method over a short period of time

Reproducability

• Precision of results obtained by different people using different but equal equipment and methods

Question 5

Define

Resolution

Uncertainty

Answer 5

Resolution

• is the smallest change in the quantity being measured that can be detected by an instrument

Uncertainty

• estimate attached to a measurement which characterises the range of values within which the true value is asserted to lie

Question 6

Define

Validity

Answer 6

Validity

• Is applicable to a measurement or whole investigation
  
  • E.g. An investigative procedure is valid if it is suitable to answer the question being asked.
  • A measurement is valid if it measures what it is supposed to be measuring

Question 7

How do you calculate percentage uncertainty?

Answer 7

% uncertainty = (2 * uncertainty in each measurement)/measurement

* 100