measurement Flashcards
What is the difference between accuracy and precision?
Accuracy is how close the measurement is to the accepted value and precision is how close the measurements are to each other
What does range provide for each set?
The range provides the amount of variability that can be seen when trying to measure the accuracy of a data set
Calculate deviation
Deviation= trial - average
Calculate average of deviations
avg of deviations = sum of dev / number of samples
What is the difference between negative and positive deviation?
Positive deviation means that there is variation between the data sets and negative deviations means that there isn’t much variation between data sets
Does the average of deviations tell you anything about the precision of the individual measurements?
No, the avg of the dev doesn’t tell anything about the precision of individual measurements because the results will be zero or a number close to zero
How can you get more valuble information from the individual deviations?
By squaring the deviations
How does the squaring of the sum of dev compare to the sum of deviations?
The sum of deviations squared gives a more precise measurement
Standard Deviation
STEV = square root of (sum of dev)^2 / n-1
What is the percent coefficient of variation?
The %CV tells you something about the measurement precision or how reproducible a measurement is
Percent coefficient of variation
%CV = STEV / average x 100%
What do you use when measuring accuracy?
Average and range
What do you use when measuring precision?
STDEV and %CV
