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31 Cards in this Set
- Front
- Back
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How many peaks does a biomodal curve have?
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2
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What is validity?
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The ability of a test or measurement to correctly identify the variable or disease it is supposed to measure (the accuracy)
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What is reliability?
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The degree to which the repeated results of a measurement will be the same (the repeatability)
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What are the two components of validity?
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Sensitivity and Specificity
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What is sensitivity?
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The ability of a test to correctly identify those who have a disease. (the percent of cases correctly identified as cases)
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What is specificity?
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The ability of a test to correctly identify those who do not have a disease (percent of non-case correctly identified as non-cases)
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What is a gold standard test?
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A more definitive test or procedure that will accurately determine whether a person actually has the disease or not
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What is the true and false negatives/positives calculation for Sensitivity?
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TP/(TP+FN)
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What is the true and false negatives/positives calculation for Specificity?
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TN/(FP+TN)
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Sensitivity is the percent of those whose outcome is:
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people with the disease for which the test is positive
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Specificity is the percent of those whose outcome is:
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those without the disease for which the test is negative
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Cut off levels need to be made for health screening tests with what type of variables?
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Continuous
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In continuous variables, if sensitivity is increased, what happens to specificity?
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Decreases
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In continuous variables, if the specificity is increased, what happens to the sensitivity?
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Decreases
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What is PPV?
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Positive Predictive Value
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What is the PPV of a test?
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The proportion of patients who test positive on a test who actually have the disease in question
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What is the calculation for PPV?
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PPV = true positives/total positives (meaning both true and false positives)
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NPV can be calculated by:
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NPV = true negatives/total negatives (meaning both true and false negatives)
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Reliability refers to what?
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Whether the results obtained on a test can be replicated if the test is repeated
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3 factors that contribute to lack of reliability:
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1. Intrasubject variation
2. Intraobserver variation 3. Interobserver variation |
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What is intrasubject variation?
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Variation of biological characteristics within individual subjects
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What is intraobserver variation?
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Variation that occurs when the same person (observer) interprets the same test results on separate occasions.
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The greater the subjective element in the reading, the greater the what?
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Intraobserver variation in the readings is likely to be
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What is interobserver variation?
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Variation between observers. Two examiners may not interpret a test result in the same manner
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Overall percent agreement is a way to evaluate what?
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Reliability
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What is the calculation for overall percent agreement?
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(a+b)/(a+b+c+d) x 100
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What is the calculation for percent positive agreement?
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(a)/(a+b+c) x 100
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What does the Kappa statistic do?
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It helps to explain to what extent does the agreement between two observers exceed the level of agreement that would result just from chance
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What does > 0.75 state in the kappa statistic?
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That there is excellent agreement beyond chance
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What does 0.40 to 0.75 state in the kappa statistic?
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Intermediate to good agreement
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What does < 0.40 state in the kappa statistic?
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Poor agreement
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