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Biostats boards

QuestionAnswer
Positive predictive value TP/(TP + FP). Probability that person actually has the disease given a positive test result
Negative predictive value TN/(TN + FN) Probability that person actually is disease free given a negative test result.
What happens to PPV when there is a low incidence Low incidence --> low positive predictive value
Sensitivity TP/(TP + FN)Proportion of all people with disease who test positive.
Use a test with high sensitivity/specificity when there is low prevalence? High sensitivity`
Use a test with high specificity/sensitivity as a confirmatory tests after a poitive screen High specificity
Type I error = False positive/false negative? Type 1 error = false positive. Stating that there is an effect or difference when none exists. (to reject null and mistakenly accept the experimental)
Type II error = false positive/false negative? Type II error = false negative. Statin that there is not an effect or difference when one exists
Probability that there is a difference between two groups despite the study's failure to show the difference? Type II error
To mistakenly reject the null hypothesis? Type I error
To mistakenly fail to rejcet the null hypothesis? Type II Error
Stating that there is an effect or difference when none exists Type I error
Stating that there is not an effect or difference when one does exist Type II error
Probability of rejecting the null hypothesis when it is in fact false Power (1-beta)
Liklihood of finding a difference when there is one Power (1- beta)
Confidence interval that spans over 0. Is Ho rejected? not significant. Not rejected (no difference)
Confidence interval for odds ratio, relative risk includes 1. Ho rejected? Not significant. Not rejected
if CI between 2 groups overalps, then are these groups significantly different? Not significanly different
Measure teh extent to which the sample means devated from the true population mean SD/square root nSEM decreases as n increases (as you increase the number of people there will be less variability)
1 standard devation = ___ %, 2 standard deviation ____%, 3 Standard deviation = ___% 1 SD: 68 %, 2 SD = 95%, 3 SD = 97%
Relative risk Proportion of diseased in exposed/diseased in unexposed (a/a+b)/(c/(c+d))
Odds ratio Odds of having disease in exposed vs. odds of having disease in unexposed (ad/bc) or (a/b)/(c/d)
Attributable risk Difference in risk between exposed and unexposed
Type of error: occurs when group being studied changes its behavior to meet expectations of researcher Hawthorne effect
Error: occurs when a researcher's belief in the efficacy of a treatment changes the outcome of that treatment Pygmalian effect
Created by: ddecampo
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