Laboratory Performance Analysis Quiz

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Questions and Answers

Which term describes the agreement between your value and the ‘true’ value?

  • Specificity
  • Accuracy (correct)
  • Precision
  • Sensitivity

Precision refers to the correctness of a single measurement.

False (B)

What is the term used to describe the reproducibility of your results?

Precision

Accuracy is determined by direct comparison to a __________ value.

<p>reference</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Accuracy = The agreement with the true value Precision = The reproducibility of results Sensitivity = The ability to correctly identify true positives Specificity = The ability to correctly identify true negatives</p> Signup and view all the answers

What consequence may arise from a lack of specificity in a test?

<p>Both A and C (D)</p> Signup and view all the answers

Poor precision can result from poor quality reagents.

<p>True (A)</p> Signup and view all the answers

What is the primary ability of a method that defines its specificity?

<p>The ability to measure solely the component of interest</p> Signup and view all the answers

A test's __________ reflects its ability to detect small quantities of a measured component.

<p>sensitivity</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Precision = The closeness of measurements to each other Accuracy = The closeness of a measurement to the true value Specificity = Ability to measure solely the target component Sensitivity = Ability to detect small quantities of an analyte</p> Signup and view all the answers

What is a key indicator of precision in measurements?

<p>The closeness of repeated results (A)</p> Signup and view all the answers

Intra-assay precision refers to the reproducibility of results within one test run.

<p>True (A)</p> Signup and view all the answers

What are the two ways in which precision is assessed?

<p>Intra-assay precision and inter-assay precision.</p> Signup and view all the answers

The ideal situation in accuracy and precision is when results are _____ and the mean is close to the ‘true’ value.

<p>accurate</p> Signup and view all the answers

Which example describes a situation that is imprecise but still accurate?

<p>Results are widely spread but the mean is close to the true value. (A)</p> Signup and view all the answers

Labs can efficiently waste resources on repeat runs if they are not achieving acceptable accuracy.

<p>False (B)</p> Signup and view all the answers

What is the significance of having precise test results for a lab?

<p>It increases confidence in the accuracy of test results and reduces the need for repeat tests.</p> Signup and view all the answers

Match each term with its definition:

<p>Accuracy = Closeness of results to the true value Precision = Closeness of repeated measurements Intra-assay Precision = Reproducibility within the same test run Inter-assay Precision = Reproducibility across different test runs</p> Signup and view all the answers

What does diagnostic sensitivity refer to?

<p>The ability of a test to detect a given disease or condition (A)</p> Signup and view all the answers

The mean of a normal distribution is also known as the median.

<p>True (A)</p> Signup and view all the answers

What is the purpose of determining diagnostic specificity?

<p>To correctly identify the absence of a disease.</p> Signup and view all the answers

The _____ is defined as the square root of the sum of the squared deviations from the mean.

<p>Standard Deviation</p> Signup and view all the answers

What does the coefficient of variation indicate?

<p>The ratio of the standard deviation to the mean (B)</p> Signup and view all the answers

A high standard deviation indicates that the values are closely clustered around the mean.

<p>False (B)</p> Signup and view all the answers

Match the following diagnostic terms with their definitions:

<p>Sensitivity = Ability to detect positives Specificity = Ability to detect negatives False Positive = Test result indicating disease when none is present False Negative = Test result indicating no disease when it is present</p> Signup and view all the answers

In a normal distribution, values fall randomly about the _____ value.

<p>mean</p> Signup and view all the answers

What does a lower standard deviation indicate about precision?

<p>More precision (C)</p> Signup and view all the answers

68% of all results are expected to fall within ± 2 standard deviations from the mean.

<p>False (B)</p> Signup and view all the answers

What is the formula for calculating standard deviation?

<p>SD = sqrt(Σ(xi - x)² / (n - 1))</p> Signup and view all the answers

The mean result in this example is _____ mmol/L.

<p>100</p> Signup and view all the answers

Match the standard deviation range to their corresponding percentages.

<p>± 1 SD = 68% of results ± 2 SD = 95% of results Mean = 100 mmol/L SD = 1.0 mmol/L</p> Signup and view all the answers

If the standard deviation is 1.0 mmol/L, what is the range within which 68% of the results fall?

<p>99 – 101 mmol/L (B)</p> Signup and view all the answers

Statistically, it is acceptable for 10% of results to fall outside of ± 2 standard deviations from the mean.

<p>False (B)</p> Signup and view all the answers

The number of results in this example is _____ .

<p>100</p> Signup and view all the answers

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Study Notes

Laboratory Performance Analysis

  • Accuracy refers to how close a measured value is to the true value.
  • Precision describes the reproducibility of measurements, meaning how close repeated measurements are to each other.
    • Within-run precision (intra-assay precision) assesses precision within a single analytical run.
    • Between-run precision (inter-assay precision) assesses precision across different analytical runs.
  • Specificity indicates the ability of a method to measure only the intended analyte, minimizing interference from other substances.
  • Sensitivity refers to the method's ability to detect small quantities of the analyte.

Common Quality Control Terms

  • Quality Control (QC) involves procedures and processes used to ensure the accuracy and reliability of laboratory results.

Statistical Concepts for Quality Control

  • Normal Distribution describes the spread of data points around a central average, known as the mean.
  • Standard Deviation (SD) represents the average dispersion of data points from the mean.
    • A lower SD indicates better precision.
  • Coefficient of Variation (CV) is the ratio of the SD to the mean, expressed as a percentage.
    • It provides a standardized measure of precision, regardless of the specific units of measurement.

Interpreting Statistical Data for Precision

  • Mean ± 1 SD: Approximately 68% of data points fall within one standard deviation of the mean.
  • Mean ± 2 SD: Approximately 95% of data points fall within two standard deviations of the mean.

Solving Precision and Accuracy Problems

  • Poor accuracy is often caused by calibration issues, which are usually easier to address.
  • Poor precision can have various causes, such as:
    • Poor quality reagents
    • Improperly maintained instruments
    • Inadequate training

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