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62 Cards in this Set
- Front
- Back
Descriptive Statistics |
Summarize a data set into a few numbers that represent or describe a group of numbers. Mean |
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Inferential Statistics |
Compare information from one set of data to another set of data to make a comparison or inference about the data T-test or linear regression |
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Population |
the entire group of items that could possibly be measured Represented by N |
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Sample |
A subset from the population. Should be randomly selected to accurately represent the population Represented by n |
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Variable |
the characteristic you want to measure |
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data |
the values you obtain from a sample population A single value is call a datum |
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data set |
set of variable connected |
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experiment |
a planned activity whose result yield a data set |
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parameter |
a numerical value that summarizes one aspect of the data from a population |
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Statistic |
a numerical value that summarizes one aspect of the data from a sample |
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Qualitative |
Yes/No values pos/neg less than greater than |
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Quantitative |
an actual number |
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Accuracy |
the measurement closest to the true value Inaccuracy: lack of closeness to the true value |
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Precision |
the repeatability of the process how reproducible are your values |
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Inaccuracy and Variability |
Inaccuracy must be detectable and is accepted within it's defined limits variability: is expected and accepted within defined limits
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Variability |
We must decide what is acceptable In the lab we test QC and use QC rules to do this |
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Qualitative Data |
Gives a general impression:
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Ways to show quantitative data |
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Frequency distribution |
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Histogram |
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Meanm Median, Mode |
In a perfect distribution they should be the same |
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Mean |
add all the numbers divided by the number of data |
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Median |
Middle number Even set of numbers divide by 2 Odd set of number (n+1)/2 Not effected by extreme values |
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Mode |
the number, or numbers, that occur the most frequently Some data is bimodal, sometimes there is no modal number not effected by extreme values |
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Measures of variability- Gaussian distribution |
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Measures of variability-Standard deviation and variance |
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Coefficient of Variation |
The smaller the CV the better the precision |
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Shift from the mean |
systematic error Can fix |
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5 stages of QC |
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Why test QC material |
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QC material- Selection and USe |
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Assayed control |
QC material that has been repeatedly analyzed by the manufacturer: Includes means and SDs Statistical data is supplied with the QC material Expensive |
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Unassayed controls |
have not been tested for concentration or variability |
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For all controlled material |
The mean and the SD must be verified or established in your lab before use in your QC program QC with different lot # may have different analyte concentrations |
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New lot # |
New mean and SD must be established |
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Minimum QC |
two levels per day for each analyte |
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Frequency of QC testing |
Instrument Manufacturer sets Experience dictates frequency of QC Criticality of the analyte dictates frequency |
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QC levels |
Normal: Ref range Below: the normal/ref range Above: the normal/ref range |
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QC level 1 |
usually in the "normal/ref range" |
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QC level 2 |
usually in the abnormal range ( some high some low) |
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QC level 3 |
Low abnormal, normal, and high abnormal- used in hematology for drug testing |
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Evaluation of QC data |
Based on Gaussian Curve:
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Levey-Jennings Chart |
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Creating a Levey-Jennings Chart |
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Analytic Errors |
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Random Errors |
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Systemic Error |
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Gaussian distribution |
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Shift |
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Trend |
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Shift/Bias |
The QC data shifts/move abruptly away from the mean for number of days |
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Trend |
QC data either decreases or increases consistently over a period of 7 days |
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Westgard QC multi-rules |
IDs the presence of:
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One (1) QC warning rule |
gets your attention |
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Five (5) QC failure rules |
used to reject qc data: 5 rules are applied if 2 QC levels are used, other rules exist if 3 qc levels are used |
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Why repeat QC with a 13s QC error |
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Why troubleshoot QC with a 22s error |
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Troubleshoot QC Systemic error |
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41s error |
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10x failure rule |
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Look at QC rules when |
QC violates the 1-2s warning rule, look at QC data continually |
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Common mistakes in use of QC |
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