Clinical Sensitivity Chemistry Quiz 1

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Questions and Answers
  • 1. 

    During diagnostic accuracy studies in evidence-based laboratory medicine, a laboratory test being studied, for example, produces results that are compared with the "gold standard" of testing, which would be the currently used assay or assay system. The test method of interest is referred to as...

    • A.

      Candidate/reference method

    • B.

      Reference standard

    • C.

      Outcome study

    • D.

      Practice test

    Correct Answer
    A. Candidate/reference method
    Explanation
    In diagnostic accuracy studies, a laboratory test being studied is compared to the currently used assay or assay system, which is considered the "gold standard" of testing. The test method being studied is referred to as the candidate/reference method because it is a potential alternative to the current standard. This term emphasizes that the method is being evaluated as a possible replacement or improvement upon the existing method.

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  • 2. 

    Another way that "bias" can be defined is as _________errror.

    • A.

      Random

    • B.

      Systematic

    • C.

      Analytical

    • D.

      Clinical

    Correct Answer
    B. Systematic
    Explanation
    Bias can be defined as systematic error because it refers to a consistent deviation from the true value or result in a study or experiment. Systematic error occurs when there is a flaw in the design, methodology, or data collection process that consistently affects the results in a particular direction. This is different from random error, which is unpredictable and can occur by chance. Therefore, systematic error is the most appropriate term to describe bias in this context.

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  • 3. 

    A new hormone analyzer is recieved in the lab. By assaying a control sample 50 times and assessing the mean and variance of the results, you are checking the___________ of the instrument.

    • A.

      Sensitivity

    • B.

      Accuracy

    • C.

      Validity

    • D.

      Precision

    Correct Answer
    D. Precision
    Explanation
    By assaying the control sample multiple times and calculating the mean and variance of the results, you are checking the precision of the instrument. Precision refers to the consistency and reproducibility of the measurements obtained from the instrument. In this case, by assessing the mean and variance, you are determining how closely the results are clustered around the average value, which indicates the precision of the hormone analyzer.

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  • 4. 

    In setting the criteria for a delta check for a specific patient, which of the parameters listed below need to be considered?

    • A.

      Specificity of the test

    • B.

      Diagnosis

    • C.

      Physiological variation

    • D.

      Sensitivity of the test

    Correct Answer
    C. Physiological variation
    Explanation
    In setting the criteria for a delta check for a specific patient, it is important to consider physiological variation. This refers to the normal range of fluctuations that can occur in a patient's test results due to biological factors such as time of day, stress levels, or medication use. By taking into account physiological variation, healthcare professionals can determine the acceptable range of change in a patient's test results over time, helping to identify any significant deviations that may indicate a potential health issue.

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  • 5. 

    Prevalence affects which of the following test characteristic?

    • A.

      Specificity

    • B.

      Predictive value of a negative result

    • C.

      Detection rate

    • D.

      False positive rate

    Correct Answer
    C. Detection rate
    Explanation
    Prevalence affects the detection rate of a test. Detection rate refers to the proportion of true positive results among all individuals who actually have the condition being tested for. When the prevalence of a condition is high, the detection rate is also likely to be high because there are more individuals with the condition to be detected. Conversely, when the prevalence is low, the detection rate is likely to be lower because there are fewer individuals with the condition to be detected. Therefore, prevalence has an impact on the detection rate of a test.

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  • 6. 

    The reference interval for glucose in a healthy adult population is 4.1 to 6.1 mmol/L. A nurse is reviewing the current test result reported on a patient and compairing the result to the previous. TEST                    DATE                      DATE                         REF INTERV.                             10/1/10                   10/2/10 Glucose                  5.8                          6.4                            4.1-6.1 mmol/L Which of the following most likely accounts for the apparent increase in the patients glucose result?

    • A.

      Patient is a diabetic

    • B.

      First specimen is non-fasting

    • C.

      Analytical variation

    • D.

      Second specimen non-fasting

    Correct Answer
    A. Patient is a diabetic
    Explanation
    The most likely explanation for the apparent increase in the patient's glucose result is that the patient is a diabetic. Diabetics often have higher glucose levels compared to a healthy adult population. This is because their bodies either do not produce enough insulin or do not use it effectively, leading to elevated blood sugar levels. Therefore, it is expected that a diabetic patient would have a higher glucose result compared to the reference interval for a healthy adult population.

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  • 7. 

    Which of the following statements is incorrect in comparing the above two calibration curves? (Refer to test for diagram)

    • A.

      Method A is more analytically sensitive

    • B.

      Method B slope is less than that of Method A

    • C.

      Method B has a better analytical response

    • D.

      Method A product has a higher molar absorptivity

    Correct Answer
    C. Method B has a better analytical response
    Explanation
    The statement "Method B has a better analytical response" is incorrect in comparing the two calibration curves. The analytical response of a method is determined by its sensitivity and slope. From the given information, it is stated that Method A is more analytically sensitive, indicating that it has a better analytical response. Therefore, the correct answer is that Method B does not have a better analytical response.

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  • 8. 

    The student T-test...

    • A.

      Compares a sample mean to a population mean using the population total

    • B.

      Compares the means of two samples using sample statistics

    • C.

      Assesses the means of samples before and following some intervention

    • D.

      Assesses the significance of difference between more than two variables

    Correct Answer
    B. Compares the means of two samples using sample statistics
    Explanation
    The student T-test compares the means of two samples using sample statistics. This means that it is used to determine if there is a significant difference between the means of two groups based on the data collected from those groups. It is a common statistical test used in research and experiments to compare the effectiveness of different treatments or interventions. By comparing the means of the two samples, the T-test helps to assess if there is a statistically significant difference between them.

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  • 9. 

    Which one of the following pre-analytical factors must be standardized when establishing a reference interval for an analyte?

    • A.

      Location (building, city, ect) in which the venipuncture is performed

    • B.

      The method of specimen collection

    • C.

      Reagents used in analyte analysis

    • D.

      The specific method used for analysis

    Correct Answer
    B. The method of specimen collection
    Explanation
    The method of specimen collection must be standardized when establishing a reference interval for an analyte. This is because different methods of specimen collection can introduce variability in the results, which can affect the reference interval. Standardizing the method of specimen collection ensures consistency in the way samples are collected, minimizing the potential for variability and allowing for accurate interpretation of the reference interval.

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  • 10. 

    Calculate the clinical sensitivity for the following data:   In a group of 80 patients diagnosed with sickle cell disease, 72 tested positive for it. The clinical sensitivity of this test is...

    • A.

      111 %

    • B.

      100 %

    • C.

      90 %

    • D.

      75 %

    Correct Answer
    C. 90 %
    Explanation
    The clinical sensitivity is calculated by dividing the number of true positive results (patients who tested positive for the disease) by the total number of patients diagnosed with the disease. In this case, there were 72 true positive results out of 80 patients diagnosed with sickle cell disease. Therefore, the clinical sensitivity is 90%.

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  • 11. 

    Which of the following statements provides the best definition for assayed control?

    • A.

      A substance that can be accurately weighed or measured to produce a solution of an exactly known concentration

    • B.

      A substance of lower purity whose concentration is determined by assay and comparison

    • C.

      Substance with an assigned value that the manufacturer establishes by using a reference method or by using reference materials traceable to primary standards

    • D.

      Substance with an assigned value used to set the value report by the laboratory's method or instrument

    Correct Answer
    C. Substance with an assigned value that the manufacturer establishes by using a reference method or by using reference materials traceable to primary standards
    Explanation
    Assayed control refers to a substance with an assigned value that the manufacturer establishes by using a reference method or by using reference materials traceable to primary standards. This means that the manufacturer determines the value of the substance by comparing it to established standards or methods. This ensures the accuracy and reliability of the substance's concentration.

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  • 12. 

    Regarding LIS, a "bidirectional interface" between LIS and a chemistry analyzer's computer means the...

    • A.

      Laboratorian must enter results directly into both the LIS and the analyzer

    • B.

      Analyzer and the LIS can communicate ordering information and test results between them

    • C.

      Analyzer can only communicate with the lis, but the LIS cannot communicate with the analyzer

    • D.

      LIS can only communicate with the analyzer, but the analyzer cannot communicate with the LIS

    Correct Answer
    B. Analyzer and the LIS can communicate ordering information and test results between them
    Explanation
    A bidirectional interface between LIS and a chemistry analyzer's computer means that the analyzer and the LIS can communicate ordering information and test results between them. This allows for seamless data transfer and eliminates the need for the laboratorian to manually enter results into both systems. The bidirectional interface enables efficient and accurate communication between the analyzer and the LIS, streamlining the workflow in the laboratory.

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  • 13. 

    The results from QMPLS on the last chemistry survey reported that for calcium your laboratory reported a value of 2.55 mmol/L where the group mean for your method was 2.50 mmol/L. The value for standard deviation interval cal (SDI) is...

    • A.

      .02

    • B.

      1.02

    • C.

      0.05

    • D.

      0.75

    Correct Answer
    A. .02
    Explanation
    The value for standard deviation interval cal (SDI) is .02. This can be determined by subtracting the group mean (2.50 mmol/L) from the laboratory reported value (2.55 mmol/L). The difference between these two values is .05 mmol/L. Since the SDI represents the range within which the laboratory value can deviate from the group mean, we divide .05 by 2 to get .025 mmol/L. Rounding this to two decimal places gives us .02 mmol/L, which is the correct answer.

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  • 14. 

    An example of a random error would be...

    • A.

      Contaminated reagents

    • B.

      Pipetting error

    • C.

      Inappropriate preparation of calibrators

    • D.

      Low volume reagent blanks

    Correct Answer
    B. Pipetting error
    Explanation
    A pipetting error refers to a mistake made during the process of transferring liquids using a pipette. This can include inaccurately measuring the volume, spilling or splashing the liquid, or not properly following the pipetting technique. Such errors can introduce variability and inconsistency in the measurements, leading to random errors in the data.

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  • 15. 

    Using an incorrect colored-stopper tube to obtain a blood sample is referred to as a(n)___________ variable.

    • A.

      Statistical

    • B.

      Analytical

    • C.

      Pre-analytical

    • D.

      Controlled

    Correct Answer
    C. Pre-analytical
    Explanation
    Using an incorrect colored-stopper tube to obtain a blood sample is referred to as a pre-analytical variable. This means that the error occurs before the actual analysis of the blood sample takes place. The choice of the tube color is important as it indicates the type of additive or anticoagulant present in the tube, which can affect the accuracy and reliability of the test results. Therefore, using the wrong colored-stopper tube can introduce variability in the pre-analytical phase of the testing process.

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  • 16. 

    In regard to a gaussian distribution +(-) 2SD's from the mean encompasses ____________ of values.

    • A.

      99.7 %

    • B.

      98.0 %

    • C.

      95.5 %

    • D.

      68.2 %

    Correct Answer
    C. 95.5 %
    Explanation
    In regard to a gaussian distribution, +(-) 2 standard deviations from the mean encompasses 95.5% of values. This is because in a normal distribution, approximately 95.5% of the data falls within two standard deviations of the mean.

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  • 17. 

    Test results were obtained on 100 healthy volunteers. The frequency versus test results were plotted. The histogram was non-Gaussian. What statistical method is applied to calculate the reference interval for the healthy population?

    • A.

      Mean +/- 2SD

    • B.

      Plot cummulative frequency versus test value on probability paper and determine test values at 2.5 % and 97.5 %.

    • C.

      Establish test value by Receiver Operator Characteristic (ROC)

    • D.

      Establish value using Likelihood Ratio Calculations

    • E.

      Plot log frequency versus test values and determine values at 2.5 % and 97.5 %

    Correct Answer
    B. Plot cummulative frequency versus test value on probability paper and determine test values at 2.5 % and 97.5 %.
    Explanation
    The correct answer is to plot cumulative frequency versus test value on probability paper and determine test values at 2.5% and 97.5%. This method is commonly used to calculate the reference interval for a healthy population. By plotting the cumulative frequency on probability paper, the distribution of the test results can be assessed. The 2.5% and 97.5% test values correspond to the lower and upper bounds of the reference interval, respectively. This method takes into account the non-Gaussian nature of the histogram and provides a robust estimate of the reference interval for the healthy population.

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  • 18. 

    Discriminator values are associated with...

    • A.

      Tests with high sensitivity

    • B.

      Tests with high sensitivity towards a specific disease

    • C.

      Tests with high specificity and low FPR towards a specific disease

    • D.

      Tests with high sensitivity and low FPR towards a specific disease

    Correct Answer
    D. Tests with high sensitivity and low FPR towards a specific disease
    Explanation
    Discriminator values are associated with tests that have high sensitivity and low false positive rate (FPR) towards a specific disease. Sensitivity refers to the ability of a test to correctly identify individuals who have the disease, while FPR refers to the rate at which the test incorrectly identifies individuals without the disease as positive. Therefore, tests with high sensitivity and low FPR are ideal for accurately detecting a specific disease without too many false positive results.

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  • 19. 

    The ROC is a statistical tool to calculate a test discriminator value that has...

    • A.

      Highest sensitivity

    • B.

      Highest specificity

    • C.

      Lowest FPR

    • D.

      Only A and C

    • E.

      Only B and C

    Correct Answer
    D. Only A and C
    Explanation
    The ROC (Receiver Operating Characteristic) curve is a statistical tool used to evaluate the performance of a binary classification model. It plots the true positive rate (sensitivity) against the false positive rate (FPR) at various classification thresholds. The highest sensitivity value on the ROC curve represents the highest ability of the model to correctly identify positive cases. Additionally, the lowest FPR value indicates the lowest rate of incorrectly classifying negative cases as positive. Therefore, the correct answer is "Only A and C" because it includes the options that correspond to the highest sensitivity and lowest FPR.

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  • 20. 

    In which of the following computer devices is the content lost each time the computer is turned off.

    • A.

      ROM

    • B.

      CPU

    • C.

      RAM

    • D.

      Hard drive

    Correct Answer
    C. RAM
    Explanation
    RAM stands for Random Access Memory. It is a type of computer memory that is volatile, meaning its content is lost each time the computer is turned off or restarted. RAM is used to temporarily store data that the computer needs to access quickly, such as running programs and open files. When the computer is powered off, the data stored in RAM is erased, which is why it is often referred to as "temporary memory." Unlike ROM (Read-Only Memory) or the hard drive, RAM cannot retain data without a continuous power supply.

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  • 21. 

    What is the specificity of the test? Patient population                              PSA Test results (>10ng/ml)                     PSA Test results (<10ng/ml) Patients with prostate cancer                               65                                                                    6 Healthy population                                                 56                                                               785

    • A.

      90.5 %

    • B.

      89.8 %

    • C.

      93.3 %

    • D.

      96.7 %

    Correct Answer
    C. 93.3 %
    Explanation
    The specificity of a test refers to its ability to correctly identify individuals who do not have the condition or disease being tested for. In this case, the test is for prostate cancer and the specificity is 93.3%. This means that the test correctly identifies 93.3% of healthy individuals as not having prostate cancer.

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  • 22. 

    A patient's serum  (am) cortisol was higher than the (pm) value. Which of the following could explain the cortisol variation?

    • A.

      Day to day variation

    • B.

      Recent food ingested

    • C.

      Diurnal variation

    • D.

      Delay in separating specimen

    • E.

      Specimen not stored properly

    Correct Answer
    C. Diurnal variation
    Explanation
    Diurnal variation refers to the natural fluctuation in hormone levels throughout the day. Cortisol levels typically follow a diurnal pattern, with higher levels in the morning and lower levels in the evening. Therefore, it is expected that a patient's serum cortisol level would be higher in the morning compared to the evening. This explains the cortisol variation observed in the patient's serum cortisol levels.

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  • 23. 

    Analytical sensitivity is related to...

    • A.

      Lowest concentration of analyte that can be detected and accurately quantitated

    • B.

      The minimum cross reactivity with other analyses with smiler structures

    • C.

      Highest concentration of analyte that can be detected and accurately quantitated

    • D.

      The highest cross reactivity with other analyses with similar structures

    • E.

      Following statement is untrue

    Correct Answer
    A. Lowest concentration of analyte that can be detected and accurately quantitated
    Explanation
    Analytical sensitivity refers to the lowest concentration of analyte that can be detected and accurately quantitated. This means that it is the minimum amount of the analyte that can be reliably measured by the analytical method. The other options, such as the minimum cross reactivity with other analyses and the highest concentration of analyte, are not related to analytical sensitivity. Therefore, the statement "Lowest concentration of analyte that can be detected and accurately quantitated" is true and the other options are false.

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  • 24. 

    Method selectivity/specificity is related to...

    • A.

      Accuracy of method

    • B.

      Reproducibility of the method

    • C.

      Degree is to which the method is free from interference by other species in the sample

    • D.

      Lowest concentration that can be quantitied accurately

    Correct Answer
    C. Degree is to which the method is free from interference by other species in the sample
    Explanation
    Method selectivity/specificity refers to the degree to which a method is free from interference by other species in the sample. This means that a selective or specific method will only measure the analyte of interest without being affected by other components present in the sample. It ensures that the method accurately identifies and quantifies the target analyte without any interference from impurities or other substances. Therefore, the answer is the degree to which the method is free from interference by other species in the sample.

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  • 25. 

    The assayed control value for creatinine is stated as 220 umol/L. The value obtained on the analyzer was 200 umol/L. What is the percent accuracy (error)?

    • A.

      -9.1

    • B.

      10.2

    • C.

      -10.2

    • D.

      20

    Correct Answer
    A. -9.1
    Explanation
    The percent accuracy (error) can be calculated by subtracting the value obtained on the analyzer (200 umol/L) from the assayed control value (220 umol/L), dividing the result by the assayed control value, and then multiplying by 100. In this case, the calculation would be: ((200-220)/220) * 100 = -9.1. This means that the value obtained on the analyzer is 9.1% lower than the expected value, indicating a negative percent accuracy (error).

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  • 26. 

    A large difference between two results of the same analyte from a single hospital patient was obtained on the same day and flagged on a chemistry analyzer result form. If the controls were in acceptable limits, what analysis should be performed on the results?

    • A.

      Critical Difference Test

    • B.

      Delta Check

    • C.

      Individual Variability test

    Correct Answer
    B. Delta Check
    Explanation
    In this scenario, a large difference between two results of the same analyte from a single hospital patient was obtained on the same day. The controls, which indicate the accuracy and precision of the analyzer, were within acceptable limits. In such cases, a Delta Check analysis should be performed on the results. Delta Check is a quality control measure that compares current results with previous results from the same patient. It helps identify any significant variations or discrepancies that may require further investigation.

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  • 27. 

    The proportion of the population that has the particular disease being studied is: 

    • A.

      Prevalence

    • B.

      Specificity

    • C.

      Sensitivity

    • D.

      Predictive value

    Correct Answer
    A. Prevalence
    Explanation
    Prevalence refers to the proportion of the population that has a particular disease being studied. It represents the number of individuals who have the disease divided by the total number of individuals in the population. It is a measure of how common the disease is in a given population at a specific point in time.

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  • 28. 

    The term detection rate is equivalent to: 

    • A.

      Sensitivity

    • B.

      Specificity

    • C.

      High FPR

    • D.

      High predictive value

    Correct Answer
    A. Sensitivity
    Explanation
    The term detection rate is equivalent to sensitivity. Sensitivity is a statistical measure that represents the ability of a test or diagnostic tool to correctly identify individuals who have a particular condition or disease. It is calculated by dividing the number of true positive results by the sum of true positive and false negative results. Therefore, the detection rate refers to the proportion of true positive results among all the individuals who actually have the condition, which aligns with the concept of sensitivity.

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  • 29. 

    Which of the following best defines the term WAN? 

    • A.

      Computer network that connects computers and their equipment in close geographic proximity

    • B.

      Computer network that connects computers and their equipment over a large geographic area

    • C.

      Incorporates all the informational needs of the laboratory

    • D.

      Incorporates all needs of the hospital

    Correct Answer
    B. Computer network that connects computers and their equipment over a large geographic area
    Explanation
    The term WAN stands for Wide Area Network, which refers to a computer network that connects computers and their equipment over a large geographic area. This means that a WAN is used to connect computers and devices that are located in different locations or spread across a wide area, such as different offices or branches of a company. Unlike a Local Area Network (LAN), which connects devices in close proximity, a WAN allows for communication and data transfer over long distances.

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  • 30. 

    Which of the following is not considered a random error: 

    • A.

      Voltage fluctuation

    • B.

      Improperly mixed reagents

    • C.

      Imprecision in pipetting

    • D.

      Improper reagent preparation

    Correct Answer
    A. Voltage fluctuation
    Explanation
    Voltage fluctuation is not considered a random error because it is a systematic error. Random errors are unpredictable and can occur in any direction, whereas systematic errors consistently affect measurements in the same direction. Voltage fluctuation is a consistent and predictable error that can be accounted for and corrected, making it a systematic error rather than a random one.

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  • 31. 

    Test order entry in the hospital setting usually occurs in the 

    • A.

      HIS

    • B.

      LIS

    • C.

      LAN

    • D.

      WAN

    Correct Answer
    A. HIS
    Explanation
    In the hospital setting, test order entry is typically done in the Hospital Information System (HIS). The HIS is a comprehensive electronic system that manages all aspects of patient care, including test orders, results, and other relevant information. It allows healthcare professionals to easily and efficiently enter, track, and manage test orders, ensuring accurate and timely delivery of care to patients. The Laboratory Information System (LIS) is specifically designed for managing laboratory test orders and results, while the Local Area Network (LAN) and Wide Area Network (WAN) are network infrastructures that facilitate communication and data sharing within and outside the hospital, respectively.

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  • 32. 

    Noise in the detection system is defined as: 

    • A.

      Signal obtained in response to analyte being measured in sample

    • B.

      Variation in signal due to analyte concentration

    • C.

      Variation in signal or background due to interferences

    Correct Answer
    C. Variation in signal or background due to interferences
    Explanation
    The correct answer is "variation in signal or background due to interferences". Noise in the detection system refers to any unwanted variation in the signal or background that is caused by interferences. These interferences can come from various sources such as electronic noise, environmental factors, or other substances present in the sample. This noise can affect the accuracy and reliability of the measurements, and it is important to minimize it in order to obtain accurate results.

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  • 33. 

    When comparing a potential new test with a comparitive method, one observes error that is consistently affecting the results in one direction. What is this type of error known as? 

    • A.

      Systematic error

    • B.

      Random error

    Correct Answer
    A. Systematic error
    Explanation
    Systematic error refers to an error that consistently affects the results in one direction when comparing a potential new test with a comparative method. Unlike random error, which occurs randomly and affects results in different directions, systematic error is predictable and can lead to biased results. It is important to identify and minimize systematic errors to ensure accurate and reliable data analysis.

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  • 34. 

    Calbration sensitivity can be determined using which of the following?

    • A.

      Standard Deviation

    • B.

      % analytical error

    • C.

      Slope of the calibration curve

    • D.

      Intercept

    Correct Answer
    C. Slope of the calibration curve
    Explanation
    The sensitivity of calibration can be determined by measuring the slope of the calibration curve. The calibration curve shows the relationship between the concentration of a substance and the response of the instrument. The slope of the curve represents the change in response for a unit change in concentration. A steeper slope indicates a higher sensitivity, meaning that small changes in concentration will result in larger changes in the instrument's response. Therefore, the slope of the calibration curve is a reliable indicator of the calibration sensitivity.

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