# Tagged Questions

A study design in epidemiology: a subset of a cohort study are more intensely measured at baseline, while the whole cohort is followed for outcomes. Primary analysis compares baseline experience of “controls” to baseline/follow-up experience of cases.

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### Using cohort + RFM

I would like to make a cohort analysis, using first order date and some score metric based on RFM. Build some RFM variables. Run a kmeans and classify my customer as: Inactive, shopper, and so on. ...
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### Power calculation (a posteriori) of a cohort study - R software

Does anyone know if there's any R library to calculate the power of a cohort study with n=9511 Reference: 50 year trends in atrial fibrillation prevalence, incidence, risk factors, and mortality in ...
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### Should cohort studies in diagnosis research be age-matched?

It is clear that cohort studies in epidemiology should be matched for such variables as age, gender, etc. However, cross-sectional cohort studies may also be used to assess the accuracy of a new ...
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### what need to be fixed in a contigency table

I am little bit confused as to what entry (i.e. the "total") are fixed in a contingency table in cohort study and case-control study. I was reading somewhere that different "total" are considered as "...
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### Proportion of controls in case-cohort design for survival analysis

I'm working on a study that is drawing from another very large study, and proposing a case-cohort design in order to reduce the overall number of samples we use (primarily due to cost of sample ...
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### Power of a case control test as a function of P(X=1) & P(Y=1)

For our course in statistics we had to build a simulation which would give insight in the power of a case-control study vs that of a cohort study, both trying to discover an association between 2 ...
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### Epidemiology cohort studies question

If we are conducting a cohort study of factors associated with recurrent myocardial infarctions (MI) following the first one, should our study population at baseline include subjects who had ...
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### Cohort analysis for media site

I'm trying to find a reasonable way to measure retention of a site (news site). I'm trying to do cohort analysis: I've grouped all visits by year/week, and measured the percent of users that kept ...
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### Predicting new data using a Case-cohort Proportional Hazards Model

I am fitting a Case-Cohort Proportional Harzards (CCH) model using the Survival (version 2.37-4) package in R 2.15.3. Normally with a Cox Proportional Harzards (coxPH) model, I can use the survfit ...
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### Dividing controls between two groups of cases

I have a set of data that contains cases and controls. I would like to divide the cases by a particular phenotype before running my tests, to see how these groups differ (but not necessarily to ...