Analysing QC Performance
Related Topics
Overview
The QC module allows for the performance analysis of analytical procedures used in CCLAS. Quality Control Performance Analysis is used to perform a laboratory performance evaluation. This evaluation is based on the QC samples of Standards, Blanks, Spikes, Replicates and Duplicates. The tests cover accuracy (bias), precision (repeatability) and contamination.
This application provides the chemist with the ability to calculate analytical accuracy, based on the standard samples included within normal analytical work. It can be used to review the data of standard samples stored in the quality control history tables. Graphical representation of the data is also supplied.
This application can be used to monitor and refine existing schemes or quantitatively evaluate new methods. Information gained from this analysis can be fed back to more finely turn the quality control checks. The Standard tables can be updated after careful statistical analysis is carried out.
This process is pertinent to quality control and laboratory managers who are responsible for the quality of the laboratory's analytical testing.
Whenever a result is received for a blank, standard, spike, replicate or duplicate QC sample, the result is assessed for contamination, accuracy (bias) or precision (repeatability), depending upon its QC type, and the assessment outcome of each observation is stored in the QC history repository.
The records in this repository are searched by type of QC sample, standard material or scheme, so that statistics and charts are presented for a set of observations.
Process
The analysis of QC performance is managed by the QC application.
Analysing QC performance involves searching the QC history repository either for discrete observations for a given QC type, QC code, analysis status, scheme, version, analyte and units, and optional date range, or for a summary of observations for a given QC type and code.
Searching for Discrete QC Sample Assessments
Discrete QC sample assessments hold the results and the outcomes of their QC assessment for individual observations (readings) of QC samples.
Search for discrete QC sample assessments
The criteria used to extract the discrete QC sample assessments can be save to a script file for later use.
Save the QC discrete criteria to a script file
Ignoring Discrete QC Sample Assessments for Statistics and Plots
Sometimes a discrete QC sample assessment may contain an outlier or non-typical result, and you may want to view statistics for, or plot, only typical results. Set the outliers to ignored to do this, and turn the ignore off to include them again. Ignored discrete QC sample assessments are highlighted yellow where selected and dark blue where selected.
Ignore discrete QC sample assessments for statistics and plots
Any status changes to discrete QC sample assessments, from ignore or not ignored, is saved when the changes be saved.
Save status changes to discrete QC sample assessments
Reporting Discrete QC Sample Assessments
Discrete QC sample assessments that are returned from a search can be reported.
Generate a report of discrete QC sample assessments
Plotting Discrete QC Sample Assessments
Discrete QC sample assessments that are returned from a search can be plotted in various plots. The type of plot available depends upon the QC type of the discrete QC sample assessments:
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Blank or Standard—XChart, Histogram, Cusum or Z-score plots.
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Replicate, Duplicate or Replicate/Duplicate—Scatter, Correlation, PCurve and Z-Score plots.
The information displayed on the plot, and the information displayed in the tool tip or plot area when the cursor hovers over a point or area in the plot, depends upon the selected plot type:
- XChart—Information includes the date range, expected value, mean value, std deviation and number of observations, and a plot point's tool tip includes the observation sequence number, (value), job, sample ident, date and user notes.
- Histogram—Information includes the date range, expected value, tolerance, mean value, std deviation and number of observations, and a plot area's tool tip includes the mean concentration of the interval and the percentage frequency of occurrence within the interval.
- Cusum—Information includes the date range, expected vale, tolerance, mean value, std deviation and number of observations, and a plot point's tool tip includes the observation sequence number, (value), job, sample ident date and user notes.
- Scatter plot—Information includes the date range, detection limit, limiting repeatability and number of observations, and a plot point's tool tip includes the observation sequence number, (average, absolute difference), (value 1, value 2), job, sample ident, date and user notes.
- Correlation plot—Information includes the date range, statistical detection limit, limiting repeatability, correlation coefficient and number of observations, and a plot point's tool tip includes the observation sequence number, (average, absolute difference), (value 1, value 2), job, sample ident, date and user notes.
- PCurve plot—Information includes the date range, detection limit, limiting repeatability and number of observations, and a plot point's tool tip includes the observation sequence number, (average, absolute difference), (value 1, value 2), job, sample ident, date and user notes.
- Z-Score—Information includes the date range, mean value, std deviation and number of observations, and a plot point's tool tip includes the standard deviation, value, job, sample ident, date and user notes, and a plot point's tool tip includes the observation sequence number, (value), job, sample ident, date and user notes.
Plot discrete QC sample assessments
Enter user notes for discrete QC Sample Assessments
Summarised QC sample assessments are based on a selected QC type and code.
Search for summarised blank and standard QC sample assessments
The criteria used to extract the summarised blank and standard QC sample assessments can be save to a script file for later use, for example, so that the limits for schemes, analytes and units within QC codes can be automatically saved over time, for later review.
Save the QC summary criteria to a script file
For each summarised blank and standard QC sample assessment, the number of observations (readings), mean, minimum, maximum and relative standard deviation can be saved to the related scheme, analyte and unit within the QC code. Over time, this information can be used to fine-tune the acceptable limits for QC assessment.
Save QC summary statistics to the QC code scheme analyte unit
Summarised QC sample assessments can be export to a file, the clipboard, or Microsoft ExcelTM.
Export summarised QC sample assessments
QC sample assessments often involves the running of custom forms to enhance the process.
