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49 Cards in this Set
- Front
- Back
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begins with "cases" and
looks for prior exposure among cases and among controls. |
case-control study
measure: OR |
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case-control study.
measure? |
OR.
begins with "cases" and looks for prior exposure among cases and among controls. |
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cohort study, begins with?
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the exposure.
given the exposure. exp(+)-------> how many cases? exp(-)--------> how many cases? measure: Relative risk |
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cohort study, measure?
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RR.
Risk of the exposed/risk of the unexposed. |
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twin concordance study - measures what?
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heritability
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postmarketing surveillance?
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phase IV
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large nr. of patients, randomly assigned to the new drug or placebo.
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Phase III.
Compares the new tx to the current standard of care. |
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Compares the new tx to the current standard of care. Also called: "the definitive test"
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Phase III.
large nr. of patients, randomly assigned to the new drug or placebo. |
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assesses efficacy, optimal dosing, adverse effects; which phase study?
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Phase II.
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assesses safety, toxicity, pharmacokinetics. which phase study?
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Phase I.
healthy volunteers. |
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SNOUT?
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sensitivity rules out.
If negative, it is a true negative. (if %100 sensitivity) sensitivity is used for screening in diseases with low prevalence |
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SPIN?
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Specificity rules in.
If positive, it is a true positive. (if %100 specificity) so, specificity is used as a confirmatory test after a positive test result |
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given a negative test result, probability of being true negative is:
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NPV
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given a positive test result, probability of being true positive is:
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PPV
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used for screening in diseases with low prevalence
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sensitivity
sensitivity=detection of the disease |
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used as a confirmatory test after a positive test result
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specificity
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1-false negative rate
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sensitivity
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1-false positive rate
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specificity
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prevalence equals incidence for ... diseases
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acute
(e.g. common cold) |
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for incidence calculation, shall we include current patients?
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No.
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prevalence = incidence x duration
true? |
True.
prevalence = incidence x duration |
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Pr. of getting the disease in the exposed / Pr. of getting the disease in the unexposed
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RR
(measure of Cohort studies) |
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odds of having the disease in the exposed / odds of having the disease in the unexposed
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OR
(measure of case-control studies) |
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one is proportion (probability), one is odds. OR and RR.
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OR: odds (case-control)
RR: probability (cohort) |
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if we do not make "dividing", instead if we calculate the difference between the risk of the exp. and unexp. - ANSWER TO: "how many more cases in one group?"
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Attributable risk
(risk of the exposed - risk of the unexposed) |
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the reduction of risk associated with a tx compared to a placebo
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absolute risk reduction
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1/absolute risk reduction
(absolute risk reduction: the reduction of risk associated with a tx compared to a placebo) |
NNT
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NNT?
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1/absolute risk reduction
(absolute risk reduction: the reduction of risk associated with a tx compared to a placebo) |
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the consistency and reproducability of a test
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reliability=precision
also, the absence of random variation in a test. so, random error > reduces precision. |
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trueness of measurements
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accuracy=validity
systematic error - reduces accuracy (validity) in a test. |
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random error reduces . . . . . . . in a test
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precision
(reliability) |
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systematic error reduces . . . . . . . in a test
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accuracy
(validity) accuracy (validity) = how often the test is right overall accuracy= (TP+TN) / TP+TN+FP+FN |
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accuracy (validity) = how often the test is right overall
true? |
true.
accuracy= (TP+TN) / TP+TN+FP+FN |
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subjects are not representative. which bias?
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sampling bias
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each subject has its own control (in time). which study?
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cross-over study
each subject receive intervention, but at different times. |
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randomization limits mainly this bias:
(also known as non-respondent bias) |
selection bias
also known as non-respondent bias. bias in loss to follow ups. |
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non-random assignment. which bias?
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selection bias
also known as non-respondent bias. bias in loss to follow ups. |
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mean + 1 SD ve mean - 1 SD aralığı (bell curve) % kaç?
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%68
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mean + 2 SD ve mean - 2 SD aralığı (bell curve) % kaç?
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%95
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mistakenly reject the null.
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type I (alpha) error.
Pr. (making a type I error) is p. convicting an innocent man. you sAw. p<0.05 dediydin ya, işte bu olasılık gerçekleşmiş! |
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stating that there is not a difference when one exists.
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type II error.
Pr.(making a type II error) = Beta. you were Blind. Power = 1 - beta |
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Pr. of making a type I (alpha) error is . . . . .
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p
(generally 1/20 is accepted) |
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1 - beta is
Pr.(making a type II error) = Beta. |
Power.
Pr. of rejecting the null, when it is in fact false. Sample size increases power. There is power in numbers. |
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how about statistical power in meta-analyses?
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high.
but it is prone to selection bias (study selection) |
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nr. of persons "exposed to risk" during a time period
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denominator of "incidence"
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total population "at risk" at a given point or period
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denominator of "prevalence"
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what happens to incidence and prevalence if; new effective tx is initiated?
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Incidence: NO CHANGE
Prev: DECREASES (Remember the incidence-prevalence pot) |
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what happens to incidence and prevalence if; new effective vaccine gains widespread use?
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Incidence: DECREASES
Prev: DECREASES (Remember the incidence-prevalence pot) |
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what happens to incidence and prevalence if; long-term survival rates for the disease increases?
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Incidence: NO CHANGE
Prevalence: INCREASES (Remember the incidence-prevalence pot) |
