1 Errors, Random Errors and Statistical Data in Chemical Analyses Part 1 [Sir Jameson PPT] Flashcards
Possible: __________ these errors and _____ their size with acceptable accuracy.
Minimize
Estimate
The analytical results are free of errors or uncertainties.
Impossible
Statistical calculations for use to judge the _______ of experimental measurements are many.
Quality
________ calculations for use to judge the quality of exerimental measurements are many.
Statistical
Measurements are always accomapnied by _________. The ________ always falls within a range due to uncertainty.
Uncertainty
True Value
The probable magnitude of the error defines the __________ within which the true value lies.
Limit
Data of unknwon quality are ___.
Worthless
The __________ of measurement is never known exactly.
True Value
Reliability Can Be Assessed In Several Ways
_______ of known composition can be analyzed, an the results with the known composition.
Standards
Reliability Can Be Assessed In Several Ways
__________ enhances the quality of the data.
Calibrating equipment
Reliability Can Be Assessed In Several Ways
Questions to answer before beginning an analysis:
- What is the ____ error that I can ________ in the result. No one can afford to waste time generating data that are more reliable than is needed.
Maximum
Tolerate
Measures of Central Tendency
2 types measures of the location of the middle of a distribution.
Mean
Median
_________, artithmetic mean, and average (x) are synonyms.
Mean
The Mean and Median
where __ represent the individual values of x making up a set of N replicate measurements
Xi
The Mean and Median
The symbol _______ means to add all the vlues Xi for the replicates.
EXi
it is the middle result when replicate data are arranged in order of size.
Median
Equal numbers of results are _____ and _____ than the _________
Larger and Smaller
Median
For an odd number of ________, the __ can be evaluated directly.
Data points
Median
The _______ of two or more measurement is their ________ value.
Mean
Average
For an ______, the ______ of the middle pair is used.
Odd number
Median
The median is used advantageously when a set of data contains an ___________, a result that differes significantly from others in the set.
Outliers
It describes the reproductibility of measurements; the closeness of results to each other.
Precision
It is determined by repeating the measurement on replicate samples.
Precisions
Three terms of describe the precision of a set of replicate data:
Standard Deviation
Variance
Coefficient Of Variation
It is function of the deviation from the mean di, or just th deviation, which is defined as
Precision
Precision Formula
di = | Xi - x̄|
It is closeness of results to others that have been obtained in exactly the same way.
Precision
It indicates the closeness of the measurement to its true or accepted value and is expressed by the error.
Accuracy
It measures agreement between a result and its true value
Accuracy
It describes the agreement among several results that have been obtained in the same way.
Precision
in the measurement of a quanity Xi, is given by the equation.
Absolute Error E
Absolute Error Formula
E = Xi- Xt
It is more useful quantity thant the absolute error.
Relative Error
Relative Error Formula
Er= Xi - Xt divided by Xt times 100%
An error is also expressed in parts per thousand (ppt)
Relative Error
To determine ________, we have to know the ______, and this value is exactly what are we seeking in the analysis.
Accuracy
True Value
it can be precise without being accurate and accurate without being precise
Results
