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32 Cards in this Set
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Relative risk =

Iold/Inew


Odds ratio=

Oddsold/Oddsnew


Absolute risk reduction

Iold  Inew


NNT =

1/(Iold  Inew)
OR 1/ARR 

What is efficacy? How is it calculated?

how much of the risk in control group is reduced by the new treatment.
ARR/Iold 

The odds ratio is an alternative to ___

RR


You can use relative or absolute measures of effect. Explain and when is each one useful.

Relative are very informative for causation strength.
Absolute is very informative with regards to the total risk reduction associated with a treatment 

Do relative or absolute measures measure the magnitude?

absolute


What allows you to compare both relative and absolute measures?

efficacy


Relative or absolute?
1. most relevant for etiology. 2. attributable risk. 3. most relevant to evaluate actual treatment/risk to exposed individuals. 
1. relative.
2. absolute 3. absolute 

why can't you only analyze the treatment of actual treatment when there is crossover?

violate principles of random


besides upholding randomization, why is it important to use intention to treat for analysis?

because crossover may be heavily due to adverse effects of treatment


List the three main limitations of randomized clinical controlled trials.

not always feasible of ethical.
limited generalizability. statistical uncertainty 

what is an alternative to incidence? to relative risk?



explain NNT.



compare relative, absolute, and combination factors.



think about when each is relative.

good work.


what is a parameter

When you want to know if one treatment is better, you want to know by how much this treatment is better!


is standard error bigger or smaller if you have a big sample size

smaller
inverse relationship 

describe type one error

when you think there is a difference when in fact there is not
associated with false positive and p value 

describe type II error

when you think there is no difference when in reality there IS!
associated with false negative and beta probability 

is type I or type II error more common? why?

type I error is more common because there is only one null hypothesis and many alternative hypotheses!


what is the null hypothesis in the case of ARR? In RR?

0
1 

how do you account for type I error?

in your pvalue


give the wording for the p value

the probability that the difference in our findings this large or larger from the null hypothesis would only occur __% of the time IF the null were in fact true


in order to find your pvalue what do you do to z?

you double it


give a definition for confidence interval

the range of values in which you would find your mean parameter 95% of the time


what can the CI NOT include if you want to say your null is untrue

you can't include your null hypothesis value


what three things does statistical power depend on?

magnitude of findings
set alpha value sample size 

how do you caluclate chi square

sum of ....(OE)^2 / E


how do you calculate SD?

like this!


how do you relate a p value and a z score?

Find z. Double it. This is P!
