Questions tagged [stratification]

A sampling technique in which the population of interest is partitioned into subsets ("strata") based on characteristics known at all units before sampling.

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183 views

svydesign fpc term in 2stage stratification [closed]

I am having some problems with svydesign() in R. My sample design is a 2 stage stratification. ...
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89 views

How to combine two sets of samples from an unnormalised distribution?

Imagine that I have an unnormalised distribution $P$ with density function $p(x)$ for $x \in \mathbb{R}^d$. $P$ has two well-separated modes and there are two sets of i.i.d. samples with the size $n$ ...
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What is the error of the global mean given known equal errors for each stratum?

This was asked to me by a colleague. It seems to be an easy one but I wasn't able to find the derivation online. I've added my own attempt below.
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How to resample from uneven strata

I've got records from patients with different cancers. Naturally, common cancers were registered often, and the cases in this group are then overrepresented and vice versa for the rare cancers. Let's ...
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On outcome stratified random forest, problems?

Hello Crossvalidated! I have a question that I can't figure out. I am working on building a classifier for a dichotomous outcome (0, 1). I use R for this. I used a Random Forest algorithm from the ...
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Are the precision gains from stratified sampling a free lunch?

I'm following the discussion in Field Experiments by Gerber and Green, Chapter 3 as well as these resources: http://ocw.jhsph.edu/courses/StatMethodsForSampleSurveys/PDFs/Lecture4.pdf http://home....
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Variance Reduction: “Smaller Samples Have Less Variance”

I was working on stratified sampling for variance reduction for monte carlo estimation, and I found an odd statement from this website (link posted below). The first line on his site is, "Intuitively,...
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3k views

Target versus sampled population

I'm having a difficult time understanding the difference between target population and sampled population using stratified sampling. For example, say I want to run some statistics on university ...
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How to construct confidence limits based on small stratified samples of finite populations?

Imagine a business wishes to audit its transactions. It has a database summarizing the transactions, which constitute a sampling frame for the population. It would be time-consuming and expensive to ...
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Checking for regional effects in survey that is stratified according to region

I have access to two surveys of the population in a specific country - one where the country is divided into 10 regions that are used as sampling strata, and another one where the country is divided ...
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Machine learning with weighted / complex survey data

I have worked a lot with various nationally representative data. These data sources have a complex survey design, so the analysis requires the specification of stratification and weight variables. ...
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54 views

Proof that the one-step estimator from logistic regression is the Mantel Haenszel estimator?

I was rereading some sections from the Breslow and Day IARC publication and noted the following: Clayton (1982) has shown that [the Mantel Haenszel] estimate arises at the first stage of ...
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How to adjust for confounding variables across different study periods?

I have a continuous & categorical outcome variables in three groups of patients, where the groups are defined by time periods 2010-2011, 2012-2014, 2015-2016. I found out that age and gender are ...
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461 views

Stratified random sampling when strata overlap

I am sure the title might be confusing, but here is what I am dealing with: I am running a survey at a health care center. The health center has around 15k active visitors. There are 5 departments ...
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81 views

Sample stratified according to region - how representative is this sample on the regional level?

I am doing a survey analysis of a specific country, and I am interested in comparing different regions of that country. Generally speaking (if possible), when a sample is stratified according to ...
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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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“Stratified” sampling of a population, where the subpopulations are based on a “count” instead of a category

I have a set of data that is essentially bowls with marbles in them. Each bowl can contain anywhere from 3 to hundreds of thousands of marbles. Many more bowls contain small numbers of marbles than ...
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377 views

Confidence intervals for stratified sampling

Let's suppose that I divided my population $N$ into 3 groups: $N_1$, $N_2$ and $N_3$ I used stratified sampling to get samples which are representativie for each group, let's call them $n_1$,$n_2$ ...
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What is the right-way to perform permutation-test using known outcomes?

I have been reading permutation test in Wikipedia. There is no mention about stratified permutation. Is there something like stratified permutation test? ...
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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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Is a regression model with various strata as parameters more accurate than strata sampling?

I am trying to understand the linked paper at ICSE 2008 (Namin et al. 2008). To provide an overview: A mutant is a variant program generated from a software program that has two distinct results -- ...
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Calculating Sample Size for Non-Inferiority Test in Cox Proportional Hazards Regression With Stratification

I have a binary predictor, X, in a Cox proportional hazards regression model, and I want to show that it is NOT a significant predictor. In other words, I want to show that there is not a significant ...
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How to do a stratified nonparametric test?

I'm trying to use the "coin" (conditional inference) package to perform a stratified nonparametric test for difference in distribution (for count data). I tried a stratified Mann-Whitney-Wilcoxon ...
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549 views

Stratified sampling when there are too many strata

I am working on a sampling exercise which involves both random and stratified sampling. The sampling is for a series of experiments run on multiple populations. Some experiments may run on the same ...
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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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Stratified sampling without sampling

At school we talked about stratified sampling regarding scientific studies. I thought of a similar case: Let's assume you have 4 questions for a certain number of people. Each of those people should ...
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Simple post-stratification weights in R

I just got my hands on the ANES (American National Election Studies) 2008 data set, and would like to do some simple analysis in R. However, I've never worked with this complex of a data set before ...
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Understanding stratified cross-validation

What is the difference between stratified cross-validation and cross-validation? Wikipedia says: In stratified k-fold cross-validation, the folds are selected so that the mean response value is ...
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Difference in estimating treatment effect in experiment using regression with covariates and assuming the data come from stratified experiment?

Assume I only did a completely randomized experiment (CRE), i.e., $N$ subjects, I randomly assign $N_t$ (say $N_t=N/2$) of them to the treatment group and the rest to the control group. Now, after I ...
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Random sampling with different stages

I'd appreciate some help solving this sampling issue: I have select a random sample of people for a survey in a certain country. The country is divided in 6 regions. In total, there are 981 ...
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Splitting Longitudinal Data into Training & Test Sets [closed]

I'm trying to find a simple way to split some longitudinal data into a training and test set. I'm familiar with using the Caret package in R to make stratified splits, but only with wide-form data. It ...
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Stratified sampling question

Suppose that I am conducting a questionnaire study that is trying to measure level of awareness of subjects about a programming language and find the relation of those level of awareness to working ...
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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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2k views

Techniques to sample skewed distributions

I am trying to understand and study the techniques that are available for sampling data in skewed distribution. For the purpose of the question, lets assume we have data collected from a city where we ...
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Standard Error for Sum

I am designing an algorithm for a stratified sampling on a population and then I want to find out what is the error bound for 95% confidence interval, for different sample statistic such as sum of the ...
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“Advanced” stratification of data in R [closed]

I have a data.frame with a column Material that has 7 different codes for 7 different materials: ...
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232 views

Stratified or unstratified binary data

What is the difference between unstratified and stratidied binary data? How does the logistic model look like for each of them?
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331 views

Stratified Analysis + Multiple Testing

I found this article, describing a systematic approach to stratified analysis: https://www.linkedin.com/pulse/conducting-stratified-analysis-test-confounding-navneet-dhand Test crude association ...
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623 views

Minimum sample size in each strata of stratified random sampling

I am performing stratified random sampling on a population (country) containing ~20 strata (states). I need to calculate mean of the population. I also know the proportion of the strata. My question ...
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60 views

Checking the variance formula of a combined estimator

If I have total $n$ patients with two sub-groups of size $n_1$ and $n_2$ in a clinical trial and I wish to find the variance of the estimator $\hat{S^c}(t)=\frac{n_1}{n} \times \hat{S_1}(t)+\frac{n_2}{...
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Stratified Paired T-Test for One Group

I have pre/post data where all subjects underwent the intervention. The outcome is a score. I am also looking to stratify my analysis by gender. I understand I can stratify my paired t-test in SAS via ...
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Why is random assignment important in stratified sampling?

Background I raised this question because of an argument I am having with a question from user697473 here. The title of his question is "Formal definiton of random assignment." In the post he ...
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stratified randomization in clinical trial design

we have 5 treatment groups (blank control, placebo, 3 doses drugs) and want to divide the 160 patients into 20, 20, 40, 40, 40 (1:1:2:2:2) for the 5 treatment groups. So this is like 8 blocks ...
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Standard deviation of the population

I have some trouble getting the standard deviation of a stratified sample. I have a sample of 1600 individuals that are divided into three groups (strata), with their sample mean $y$, which is the ...
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1answer
877 views

Estimation of sample size for stratified randomized clinical trial with R

We want to conduct a multi-center randomized clinical trial with two arms (2 treatments : a superiority trial) stratified on three centers (three sites). The primary outcome variable is a continuous ...
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Two sample tests for stratified randomization

I have to test the difference between two samples which were selected via stratified randomization. The problem is that the samples are not independent due to randomization was stratified. How should ...
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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 ...
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Stratified sampling if Proportion is know for each strata and overall population?

I have 4 test strata and I need to estimate sample size for each. Each strata have different proportion value (based on historical data): Stratum #1- Proportion = 0.75% Stratum #2- Proportion = 1.5% ...
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1answer
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How to weight data according to multiple variables

I have two datasets. Dataset A is considered the population. It has 7 variables with different number of classes / breaks for each. Dataset B is the dataset I want to make look like Dataset A in ...
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Relation between Stratify Sampling and Blocking

In experiment, if you know before that an attribute $X$ may affect the treatment effect, so you could do stratify sampling from your target population, e.g., if $X$ is weight, then you could divide ...