Ch 5 Errors in Chemical Analysis Flashcards
Samples of about the same size that are carried through an analysis in exactly the same way
Replicates
Is the middle value in a set of data that has been arranged in numerical order
Median
The _____ of two or more measurements is their average value
Mean
Is the closeness of results to others obtained in exactly the same way
Precision
A result that differs significantly from the others in the set. This affect the mean of the set, but no effect on the median
Outliers
What are the things that describe the precision of a set replicate data
Standard deviation, variance, and coefficient of variation
Is the closeness of a measured value to the true or accepted value
Accuracy
The difference between the measured value and the true value
Absolute error
The absolute error divided by the true value. Expressed in ppt
Relative error
This type of error affects measurement precision
Random error/ indeterminate error
This type of error affects the accuracy of result
Systematic error/determinate error
What are the three sources of systematic error
Instrumental errors
Method errors
Personal errors
An occasionally result in replicate measurements that differs significantly from the other results
Outlier
Measures the systematic error associated with an analysis
Bias
Caused by nonideal instrument behavior, by faulty calibrations, or by use under inappropriate conditions
Instrumental error
Result from the carelessness, inattention, or personal limitations of the experiment
Personal error
Arise from the nonideal chemical or physical behavior of analytical systems
Method error
Are independent of the size of the sample being analyzed
Constant errors
Increase or decrease in proportion to the size of the sample
Proportional erros
Are substances sold by NIST and certified to contain specified concentrations of one or more analytes
Standard reference materials
A solution that contains the solvent and all of the reagents in an analysis, but no analyte
Blank solution
Refers to the collection of all the constituents in the sample
Sample matrix
