Paper 3 definitions Flashcards
Accuracy
A measure of how close a measurement is to to the true value
Precision
A measure of how close a measurement is to the mean value. It only gives an indication of the magnitude of random errors, not how close data is to the true value
Random error
Unpredictable variation between measurements that leads to a spread of values about the true value. Random error can be reduced by taking repeat measurements
Systematic error
Causes all readings to differ from the true value by a fixed amount. Systematic error cannot be corrected by repeat readings, only by using a different method or equipment
Repeatable
The same experimenter can repeat a measurement using the same method and equipment and obtain the same value
Reproducable
An experiment can be repeated by a different person using different equipment and obtain the same value
Resolution
The smallest change in a quantity that causes a visible change in the reading that a measuring instrument records
Uncertainty
The interval that a value is said to lie within, with a given level of confidence
When adding or subtracting data with uncertainties
Add the absolute uncertainty
When multiplying or dividing data with uncertainties
add the percentage uncertainty
When raising data with an uncertainty to a power
multiply the percentage uncertainty by the power
Absolute uncertainty in a reading
+/- half the smallest division
if the smallest division is 1 the uncertainty is +/- 0.5
Uncertainty in a measurement
At least ±1 smallest division,
(a ruler, must include both the uncertainty for the start and end value, as each end has ±0.5mm, they are added so the uncertainty in the measurement is ±1mm)
Digital readings uncertainty
either have the uncertainty quoted or assumed to be ± the last significant digit
(3.2 ± 0.1 V)
repeated data uncertainty
half the range/the mean
