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32 Cards in this Set
- Front
- Back
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a study that is chosen based on presence or absence of disease and then information collected about risk factors
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case-control study
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a cohort study is what kind of study?
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observational
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in this type of study, the sample is chosen about presence or absence of risk factors and subjects are followed over time for development of disease
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cohort study
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define prevalence
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total cases in population at a given time/ total population
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define incidence
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new cases in population over a given time period/total population at risk during that time
incidence is new incidents |
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for what type of diseases is prevalence greater than incidence?
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chronic diseases
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for what type of diseases does prevalence equal incidence?
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acute diseases
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for what type of test is high sensitivity desirable?
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screening
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define sensitivity and give formula
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number of true positives divided by number of all people with the disease: a/a+c
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how do you calculate the false negative rate?
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1-sensitivity
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for what type of test is high specificity desirable for?
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confirmatory test
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define specificity and give formula
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number of true negatives divided by number of all people without the disease: d/b+d
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1-specificity is equal to what?
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false positive rate
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what is positive predictive value and how do you calculate it?
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probability of havinig a condition given a positive test - number of true positives divided by number of people who tested positive for the disease: a/a+b
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what is negative predictive value and how do you calculate it?
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probability of having a condition given a negative test - number of true negatives divided by number of people who tested negative for a disease: d/c+d
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which are dependent on the prevalence of disease: sensitivity/specificity or predictive values?
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predictive values
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when prevalence is higher, what increases?
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positive predictive value
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when prevalence is lower what increases?
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negative predictive value
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what is an odds ratio?
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odds of having disease in exposed group divided by odds of having disease in unexposed group (odds calculated within group as number with disease divided by number without disease)
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what is the formula for odds ratio?
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(a/b)/(c/d) = ad/bc
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what is relative risk?
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disease risk in exposed group dividd by disease risk in unexposed group - risk is calculated within a group as number with disease divided by total number of people in group
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what is the formula for relative risk?
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a/(a+b)/c/(c+d)
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what is a type I error?
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stating that there is an effect when none exists; equal to p
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what is a type II error?
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stating that there is not an effect of difference when one exists (power= 1-type II)
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what does Z equal for the 95% confidence interval?
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1.96
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what is the formula for confidence interval?
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CI=range from (mean-Z(SEM) to (mean+Z(SEM)
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what does standard error of the mean equal?
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standard deviation/square root of n
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a t-test checks the difference between what?
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the means of 2 groups
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what does ANOVA check?
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the difference between the means of 3 or more groups
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what does chi square check?
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difference between 2 or more percentages or proportions of categorical outcomes (not means)
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mean > median > mode is what kind of skew?
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positive - tail on right
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mean < median < mode is what kind of skew?
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negative - tail on left
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