Practical Skills at AS Level Flashcards
Uncertainty
the uncertainty in a reading is an estimate of the difference between the reading and true value of the quantity being measured
Precision
the smallest change in value that can be measured by an instrument or operator
Precise measurement
a measurement that is made several times giving the same or very similar values, and there is very little spread about the mean value
Accuracy
an accurate value of a measured quantity is one that is close to the true value of the quantity
Systematic error
causes readings to differ from the true value by a consistent amount each time the reading is made
Zero error
caused when an instrument given a non-zero reading when the true value of the quantity is zero
Random error
causes readings to vary around the mean value in an unpredictable way from one reading to another
Uncertainty can be found from
the largest out of either the;
smallest division on the instrument used or,
half the range of a number of readings of the measurement
Tables
Each column of a table must be labelled with a quantity/unit and if a reading be given to the precision of the instrument, usually to the same number of decimal places. Calculated quantities may have one more significant figure than the readings used
Independant variable
the one that experiment alters or selects
Dependant variable
the quantity that changes as a result of being altered by the experimenter
Best fit line
straight line drawn as closely as possible to the points of a graph so that similar numbers of points lie above and below the line
Suggested relationship
If the values differ by more than 10% the suggested relationship is not supported by the values, if they differ by less than 10% the suggested relationship is likely
