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Quiz 4b Quality management
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Terms in this set (60)
Which of the following is an example of an inferential statistic?
t test
Analysis of variance (ANOVA) is an appropriate statistics to evaluate three or more sets of data among each other.
True
Which of these reflects an appropriate selection of quality control material ?
QC1 range= 50-70 mg/dL;
QC2= 350-380 mg/dL;
AMR= 20-600 mg/dL
What is Proficiency Testing?
The assessment of a lab's performance by an outside agency.
Which of the following practices is inappropriate when establishing quality controls ranges?
Exclusion of any quality control results greater than ±2 standard deviation from the mean
When referring to quality control results, what parameter usually determines the acceptable range?
The 95% confidence interval for the mean (or +/-2SD)
Linearity is useful for assessing:
Slope and intercept of an analytical method.
Least squares, Deming's, and Passing and Bablok are examples of:
Regression analysis.
Which of the following statements best defines the term accuracy?
The closeness of the agreement between the measured value of an analyte to its true value
Board Review Question: The statistical term for the average value is the:
mean
Board Review Question: The term used to describe reproducibility is
precision
Board Review Question: A mean value of 100 mg/dL and a standard deviation value of 1.8 mg/dL were obtained from a set of glucose measurements. The 95% confidence interval in mg/dL would be:
96.4 - 103.6
Board Review Question: A glucose determination was read on a spectrophotometer. The absorbance reading of the standard was 0.30. The absorbance reading of the unknown is 0.20. The value of the unknown is :
two-thirds of the standard
Board Review Question: Given the following values: 100, 120, 150, 140, 130. What is the mean?
128
Board Review Question: Upon completion of a run of cholesterol tests, the technician recognizes that the controls are not within the two standard deviation confidence range. What is the appropriate course of action?
run a new set of controls and repeat specimens
Board Review Question: The middle value of a data set is statistically known as the
median
A man is competing in a bowling tournament. His first ball consistently hits between pins 4 and 7 resulting in five pins knocked down. Which is correct?
He has precision but not accuracy.
Which of the following is part of preventative maintenance for instruments?
Performing a series of instrument checks to reduce instrument malfunction
The ED calls and asks that the lavender tube used for conducting a complete blood count be used for potassium. What is the problem with this approach?
Potassium is the EDTA cation producing a falsely high result.
A clinical laboratory is performing a normal range study for a new test. Blood from 120 healthy volunteers produced a mean result of 100 with a standard deviation of 20. If the distribution of results are parametric (bell-shaped), what is the recommended reference range?
80-120
The reference interval is determined from the mean plus and minus two times the standard deviation. A minimum of 120 subjects is recommended.
What are controls that do not have a predetermined value for the tested analyte termed?
unassayed controls
Which of the following is true regarding proficiency testing?
Inaccurate testing or reporting can lead to sanctions taken against the lab.
The following data are daily quality control results for a QC material. The mean and standard deviation is 100 ±10. Which of the Westgard rules is violated?
Day 1: 103Day 2: 121Day 3: 79Day 4: 104
R 4s
A violation of the R 4s rule occurs when one control exceeds the mean +2 SD (day 2) and the other exceeds the mean -2 SD (day 3).
Which step proceeds "measure" in a Six Sigma sequence?
define
Which of the following is not part of a laboratory's standard operating procedure?
Qualifications of the operators
Which statistical term refers to a percentage that a laboratory test is positive in the presence of the disease?
diagnostic sensitivity
A blood sample is collected in a doctor's office and is placed on the bench for 4 hours at room temperature before it is sent to the lab for centrifugation and analysis. The results of which analyte will be greatly affected?
Glucose
Blood cells from an unspun tube will continue to metabolize glucose if a blood tube is not spun. The use of a gray tube containing sodium fluoride and potassium oxalate will inhibit glycolysis.
Board Review Question: The extent to which measurements agree with or approach the true value of the quantity being measured is referred to as
accuracy
Board Review Question: Which of the following is the formula for the arithmetic mean?
sum of values / number of values
Board Review Question: Which of the following is the formula for the coefficient of variation?
(Standard deviation x 100) / mean
Board Review Question: The following data were calculated on a series of 30 determinations of serum uric acid control: mean = 5.8 mg/dL, 1 standard deviation = 0.15 mg/dL. If confidence limits are set at 2 standard deviations, which of the following represents the allowable limits of the control?
5.50 - 6.10 mg/dL
Board Review Question: The standard deviation is the acceptable limit of error in the chemistry lab. If you run the normal control 100 times, how many of the values would be out of control due to random error?
5
Proportional error in a method is characterized by which of the following?
The magnitude of the error increases as the concentration of analyte increases.
The results of a precision study are shown below. What is the percent coefficient of variation for the study?Mean = 100 mg/dL
Standard deviation = 2.5 mg/dL
2.5%
(2.5 x 100) /100
Which of the following quality control rules means you have one point outside of 2 SD?
1 2s
A 2 2s quality control rule violation is defined as:
Two consecutive control values that exceed ± 2 s.
A glucose result that is lower than the detection limit of the method should be reported as which of the following?
Less than the detection limit value
"the measure of the dispersion of a group of values around the mean" is
the SD
Calculate the CV if the mean is 122 mg/dL and the SD is 5.2 mg/dL
4.26
(5.2 x 100) / 122
Which of the following statistics is used to qualify the strength of the relationship between two variables?
Correlation coefficient
Which of the following plots is best for detecting all types of quality control errors?
Levy-Jennings
Diagnostic sensitivity means that the disease is absent if the test is negative.
False
Which of the following is carried out during the preanalytical stage of laboratory testing?
Specimen processing
A glucose result is falsely elevated and it was discovered that the previous sample on the sample carousel has abnormally high serum glucose. Which of the following can cause this error?
Carryover
Recapping/storage/retrieval are all examples of tasks performed during which of the following?
Recapping/storage/retrieval are all examples of tasks performed during which of the following?
An important difference between parametric statistics and nonparametric statistics is that parametric statistics presumes a Gaussian distribution, whereas nonparametric statistics:
Is distribution-free, and usually comprised of nominal variables
You review your Levey-Jennings chart for the level 1 control on assay X and you notice that the data is scattered all over the chart, past the +2SD line and the -2SD line, and your CV is 9%. This is an idication of:
imprecison
A test's "negativity in the absence of the disease" is termed its:
Specificity
What is a critical value for a lab test?
A test result that indicates a life-threatening condition
What is the reason for recommending that some samples, like blood gases, lactate, and ammonia, are sent on ice?
All of these are correct.
For blood gases, it reduces the partial pressure of the gases, thereby reducing the likelihood of loss of CO2 or gain of O2.
For lactate, it reduces the activity of LDH that can falsely increase lactate levels.
For ammonia, increasing levels occur due to release from red cells and the deamination of amino acids.
Board Review Question: The mean value of a series of hemoglobin controls was found to be 15.2 g/dL, and the standard deviation was calculated at 0.20 g/dL. The acceptable control range for the laboratory is a 2 standard deviation. Which of the following represents the allowable limits for the control?
14.8 - 15.6 g/dL
Board Review Question: An index of precision is statistically known as the:
coefficient of variation
Board Review Question: The most frequent value in a collection of data is statistically known as the:
mode
Board Review Question: In quality control, a 2-standard deviation from the mean includes what percent of the sample population?
95
The statistical values that assess precision are:
INCORRECT the mean and the SD
A new method is compared against one that is in routine use. When performing a linear regression analysis, which of the following statistical parameters determines if the new test has a proportional bias?
slope
A minimum of how many QC levels should be run daily on chemistry analytes?
2
The statistical value that assesses accuracy is:
incorrect the sd
True or false? Random analytical error can be in any direction and indicates imprecision.
true
Direct tube sampling by automated analyzers eliminates the need to perform which of the following tasks?
Pour off specimens into another container
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