CLINICAL CHEMISTRY PART 2
QUESTIONS AND ANSWERS
Measures of center - Answer-mean, median, mode
The three most commonly used descriptions of the center of a dataset are the mean,
the median, and the mode.
Measures of spread - Answer-Coefficient of variation, Range, Standard deviation
The sprea...
CLINICAL CHEMISTRY PART 2 QUESTIONS AND ANSWERS Measures of center - Answer -mean, median, mode The three most commonly used descriptions of the center of a dataset are the mean, the median, and the mode. Measures of spread - Answer -Coefficient of variation, Range, Standard deviation The spread represents the relationship of all the data points to the mean. There are three commonly used descriptions of spread: (1) range (2) standard deviation (SD), and (3) coecient of variation (CV). Systematic errors: - Answer -Aging reagents Aging calibrators Instrument components Optical changes Fluctuations in line voltage Wear and tear of instrument Reagent lot variability Calibration differences Technologist interactions A SYSTEMATIC ERROR, on the other hand, will be seen as a trend in the data. Control values gradually rise (or fall) from the previously established limits. This type of error includes improper calibration, deterioration of reagents, sample instability, ins trument drift, or changes in standard materials. All the Westgard rules that indicate trends identify systematic errors. 2(2S), 4(1S) and 10(x) rule. Random errors include: - Answer -RANDOM ERROR is one with no trend or means of predicting it. Random errors include such situations as mislabeling a sample, pipetting errors, improper mixing of sample and reagent, voltage uctuations not compensated for by instrument circuitry, and temperature uctuations. Violations of the 1(2S), 1(3S) and R(4S) Westgard rules are usually associated with random error. To assess the situation, the sample is assayed using the same reagents. If a random error occurred, the same mistake may not be made again, and the result will be within appropriate control limits. RANDOM ERRORS MAY BE DUE TO: Reagent dispensing Sample evaporation Temperature of analyzer Electro -optical mechanism Calibrator reconstitution Environmental conditions Instability of instrument Variation in handling techniques: pipetting, mixing, timing Variation in operators Most frequently occurring value in a dataset: a. Mean b. Median c. Mode d. Range - Answer -c. Mode The mode is the most frequently occurring value in a dataset. Although it is seldom used to describe data, it is referred to when in reference to the shape of data, a bimodal distribution, for example. Type of systemic error in the sample direction and magnitude; the magnitude of change is constant and not dependent on the amount of analyte. a. Constant systematic error b. Proportional systematic error - Answer -a. Constant systematic error Type of systemic error where the magnitude changes as a percent of the analyte present; error dependent on analyte concentration. a. Constant systematic error b. Proportional systematic error - Answer -b. Proportional systematic error Difference between the observed mean and the reference mean: a. Bias
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