Question 1

Which of the following is true regarding proportional systematic errors?

Accepted Answer

Proportional systematic errors affect the slope of the regression line, causing it to differ from the true value, while the intercept remains unaffected.

Question 2

An automated cell counter consistently produces red blood cell readings that are 20% too low.What type of error is this considered?

Accepted Answer

The consistent and predictable nature of the error indicates that it is a systematic error.

Question 3

Using only the 1_3s rule to evaluate a control run has a low risk of falsely rejecting a run.What is a common concern about using only this rule?

Accepted Answer

The 1_3s rule focuses on identifying significant shifts or trends in data, but it may not be sensitive enough to detect smaller, more frequent errors, leading to a low rate of error detection.

Question 4

The following is a Levey-Jennings chart. 
Which of the following is the best conclusion based on the circled data?

Accepted Answer

The answer of The following is a Levey-Jennings chart. 
Which...

Question 5

A Levey-Jennings chart is created to analyze a set of data.The last consecutive eight data points gradually move downward away from the mean.What type of aberration would this be considered?

Accepted Answer

A consecutive set of data points that gradually move away from the mean is known as a trend. This type of aberration indicates a systematic shift in the data rather than a random variation (outlier) or a sudden change (shift). Variance refers to the spread of the data, which is not relevant in this case.

Question 6

What is a concern about the single rule that dictates that control values must fall within two standard deviations of the mean?

Accepted Answer

The single rule of control values falling within two standard deviations of the mean can lead to false alarms, causing rejection of acceptable testing runs, which can impact patient care. However, it is still a widely accepted rule in laboratory quality control.

Question 7

How can the effects of random error be minimized?

Accepted Answer

Averaging a large number of results can help minimize the effects of random error. This is because random error is unpredictable and can occur in any direction, so taking a large amount of measurements and averaging them can help cancel out some of the random errors. Options B, C, and D do not necessarily minimize the effects of random error.

Question 8

The following is a Levey-Jennings chart measuring a single control. 
What Westgard Rule is violated in this chart?

Accepted Answer

The answer of The following is a Levey-Jennings chart measuring...

Question 9

Which of the following explains how a violation of Westgard Rule R₄s is identified?

Accepted Answer

Westgard Rule R₄s is violated when the difference between two consecutive data points is at least 4 SD, and one data point lies above $ \bar{x}+2 s $ and the other lies below $ \bar{x}-2 s $, OR when the result from one control lies above $ \bar{x}+2 s $, and the result from a different control lies below $ \bar{x}-3 s $. Therefore, both A and C are correct.

Question 10

Which of the following is true regarding constant systematic errors?

Accepted Answer

Constant systematic errors affect the y-intercept of the regression line, causing it to differ from the true value. The slope and x-intercept, on the other hand, remain unaffected.

Question 11

One of three quality-control results for an instrument violates the 1₂s rule.What is the proper course of action?

Accepted Answer

The 1₂s rule is a quality control rule that establishes a warning limit for the instrument's performance. When a violation of this rule occurs, it indicates that the instrument's performance is outside the expected values and needs investigation. Therefore, refraining from running patient specimens until resolution of the problem is the proper course of action to avoid the potential risk of patient harm.

Question 12

Which of the following is a crucial feature of a substance used as a control?

Accepted Answer

A crucial feature of a substance used as a control is that it should mimic the chemical and physical properties of a typical patient specimen. This allows for a more accurate and reliable comparison between the test results obtained from patient samples and the control. Options A and B are not necessarily crucial features of a control, and option C is incorrect as it suggests a specific storage temperature for controls, which may not be applicable to all types of controls.

Question 13

Which of the following is true about Rule 1₂s?

Accepted Answer

Rule 1₂s, often associated with Westgard rules for quality control in clinical laboratories, implies that a control will be considered out of acceptable limits if it falls outside ±1s (standard deviation) twice in a row on the same side of the mean, among other criteria. The statement that a control will violate the rule approximately once in every 20 acceptable runs is a statistical expectation based on the normal distribution of control values, where approximately 5% of values (or 1 in 20) would be expected to fall outside of ±1s under normal circumstances.

Question 14

What are the rules,as stated by CLIA,for the number and frequency of control tests that a laboratory should run on a qualitative assay?

Accepted Answer

According to CLIA, a laboratory should run a test of one positive and one negative control at least once per day for a qualitative assay. Option A is the only choice that accurately reflects this guideline. Option B refers to controls of unknown concentrations, which may not be applicable, and option D requires two different positive controls, which may not be necessary for all tests. Option C suggests running controls at different concentrations, but does not specify the number or type of controls, so it is also not the best choice.

Question 15

Many laboratories have the policy that,in the event of a Rule 1₂s violation,the control must be repeated.If the result is in range,then patient specimens may be run.Why is this common practice controversial?

Accepted Answer

The answer of Many laboratories have the policy that,in the...

Question 16

The following plot is a Levey-Jennings chart. 
Which of the following is true about the data point noted by the arrow?

Accepted Answer

The data point noted by the arrow falls outside of the control limits, making it an outlier. It is not necessarily indicative of a shift or a trend, but rather a point that falls far from the expected range.

Question 17

Which of the following explains the primary use of Levey-Jennings charts?

Accepted Answer

Levey-Jennings charts are primarily used for identifying outliers, trends, and shifts in data that may indicate a malfunction or other problem in laboratory equipment.

Question 18

On a Levey-Jennings chart,the final single data point falls outside the +3 SD mark.According to Westgard Rule 1₃s,should the most recent run be accepted?

Accepted Answer

The Westgard rule 1₃s indicates that a single data point falling outside the +3 SD mark is a violation, leading to rejection of the run. This rule is designed to ensure data quality by identifying significant deviations from the expected range.

Quiz 11: Quality Control

Which of the following is true regarding proportional systematic errors?

An automated cell counter consistently produces red blood cell readings that are 20% too low.What type of error is this considered?

Using only the 13s rule to evaluate a control run has a low risk of falsely rejecting a run.What is a common concern about using only this rule?

The following is a Levey-Jennings chart. Which of the following is the best conclusion based on the circled data?

A Levey-Jennings chart is created to analyze a set of data.The last consecutive eight data points gradually move downward away from the mean.What type of aberration would this be considered?

What is a concern about the single rule that dictates that control values must fall within two standard deviations of the mean?

How can the effects of random error be minimized?

The following is a Levey-Jennings chart measuring a single control. What Westgard Rule is violated in this chart?

Which of the following explains how a violation of Westgard Rule R₄s is identified?

Which of the following is true regarding constant systematic errors?

One of three quality-control results for an instrument violates the 12s rule.What is the proper course of action?

Which of the following is a crucial feature of a substance used as a control?

Which of the following is true about Rule 12s?