# Tagged Questions

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### How do I address a known bias in my sample?

I have a population of interest ($N = 5000$) for which I know some demographic information. I have a sample 1500 members of that population. So I have a good sized sample, and I know exactly how it ...
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### Block randomization for different strata, how to achieve 1:1 treatment allocation

I am trying to randomize 60 patients in two treatments (A and B) where age will be used as strata. Since we don't know how many patients of each stratum will enter the study I have created two ...
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### How to determine degree of freedom for a certain test of interaction?

The scenario is like this: I have a cohort with 2000 people, half of them taking DRUG, the other half not taking it. I would like to check interactions between DRUG and the other variables in the ...
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### Stratified Sampling and the Central Limit Theorem

What can be said about the convergence rate of stratified sample means to a normal distribution, given different allocation schemes? Obviously, under very poor allocation, this convergence can fail ...
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### Nested, Stratified Ratios

I need some advice. I have a stratified sampling design by season and area. However, within any stratum the statistic I'm interested in $\hat{R} = \sum y/\sum x$ is also affected by other factors. ...
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### Multilevel model vs. separate models for each level

What are the advantages and disadvantages of running separate models vs. multilevel modeling? More particularly, suppose a study examined patients nested within doctors' practices nested within ...
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### Treatment effect Analysis: What is Stratification and explanation/interpretation?

In this paper by Angrist a stratification estimator is used (page 16 formula (4)) to calculate the Average Treatment Effect on the Treated (ATOT). The formula is given by: \begin{align} ...
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### Can I perform a stratified test againts a true value?

I have a study where they randomized patients into 2 groups (A and B). The primary aim is to compare group A against a fixed/ true value of 0.75. The binomial test is not stratified and cochran mantel ...
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### Empirical distribution alternative

BOUNTY: The full bounty will be awarded to someone who provides a reference to any published paper which uses or mentions the estimator $\tilde{F}$ below. Motivation: This section is probably not ...
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### For count data from a survey, do variance corrections for survey design imply that the Poisson distribution will not accurately model the counts?

I have categorical count data that comes from a complex survey. Each unit of analysis in the survey (household, individual, etc.) is put into one and only category per dimension, ranging from 2 to 20 ...
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### Analysis of complex sample

The company where I work did a survey with a complex sample. Originally, the sample was a 2-step stratified, but due to some problems, we lost one of them (so, let's consider that the sample is ...
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### clustered-stratified random sampling

i've got questions about clustered-stratified random sampling. let's say I want to do a research in narcotics. the population that I will be working with is a combination of academics, students, and ...
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### When do you stratify an analysis versus including an interaction term?

I’m not very familiar with when and why you would stratify on a variable or set of variables in a regression analysis generally and would like to know what the issues are particularly in contrast to ...
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### Understanding stratified CV

What is the difference between stratified CV and CV? Wikipedia says: In stratified k-fold cross-validation, the folds are selected so that the mean response value is approximately equal in all ...
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### Fisher overall p-value vs. pairwise comparisons

I am doing comparisons on response rates across three sites. Following are the cell counts ...
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### Beta coefficients from stratified analysis when there are covariates?

Suppose I have a regression model shown below Model 1: $$Y = \beta_0^\ + \beta_1SEX\ + \beta_2ALCOHOL\ + \beta_3SEX*ALCOHOL\$$ The predictors I am interested in are SEX (binary: 0 female, 1 male) ...
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### What are the optimizations or goals to consider when using stratified sampling?

In stratified sampling, what are the optimization considerations? For example, the sample size per stratum could be defined with proportional allocation as $n_h=n\frac{N_h}{N}$, where $N_h$ is the ...
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### Stratified sampling with multiple variables?

I don't know much about stats so I'm looking for a starting point here. Any resources or insights would be helpful. I'm conducting an e-learning experiment, in which students watch videos and then ...
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### Stratified Cox model

I am working on fitting a Cox model to predict. But several predictors violated the proportional hazards assumption. I am gonna to do stratified Cox model to adjust them. But the results of stratified ...
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### Bootstrapping stratified sample that is weighted to population - reweighting during the bootstrap?

I'm using R to provide bootstrap (percentile and t methods) of estimated population totals, using data from a complex survey. It is a stratified survey of tourists expenditure that is weighted to ...
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### When using stratified randomization in a RCT, how many envelopes per stratum should be prepared?

If one considers a hypothetical RCT, say a total sample size of 300, separated into three strata based on surgical procedure (open surgery, closed surgery, or combined procedure). Blocking in groups ...