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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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97 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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4k 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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1answer
55 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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154 views

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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1answer
522 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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1answer
92 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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an alternative allocation method for small RCTs?

stratification and minimization are two randomization options to achieve balance in terms of covariates or baselines in small RCTs. in recent years, researchers seem to have favoured minimization, ...
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453 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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154 views

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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59 views

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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75 views

“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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639 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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66 views

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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1answer
512 views

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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210 views

Cluster Analysis on a Stratified Random Sample

I have a set $A$ that consists of 5 million objects. Each object has a color, size and cost. I'd like to do a cluster analysis, e.g. K-means, on cost. However, it is computationally not feasible to ...
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43 views

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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1answer
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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217 views

How to partition data with multiple categorical features?

I have a data set with size of 30k+, and it has several categorical features and also several numerical features. When I try to split the data into training/testing data set, I need to answer a ...
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1answer
129 views

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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49 views

“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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1answer
191 views

Stratified Sampling Allocation

You believe that the mean electricity usage is about twice as much for houses as for apartments or condominiums, and that the standard deviation is proportional to the mean so that S1 = 2S2 = 2S3. How ...
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287 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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1answer
345 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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1answer
675 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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61 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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626 views

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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2answers
57 views

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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202 views

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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576 views

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 ...
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498 views

Stratified sampling with replacement of participants in R

I am wondering whether in R, there is a possibility to draw a stratified sample with replacement of participants. Often, in surveys, we need each group to have certain size. Hence if one respondent in ...
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1answer
17k views

Benefits of stratified vs random sampling for generating training data in classification

I would like to know if there are advantages of using stratified sampling instead of random sampling, when splitting the original dataset into training and testing set for classification. Also, does ...
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1answer
76 views

Stratification based on propensity score and a second variable

The basis of my question is whether it makes sense, given you have a set of propensity scores, to stratify the data based on the propensity scores and on a second variable which was included in the ...
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2answers
957 views

How does the boot package in R handle collecting bootstrap samples if strata are not specified but the function separates the dataset by strata?

My current understanding is 1) if strata are not specified, then boot randomly selects rows with replacement from the entire dataset. If dataset is actually stratified then boot would often return ...
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135 views

How can i Age adjust the proportions of my covariates in a multiple stratified data set?

I am doing a cross sectional analysis in a huge data set. The initial descriptive analysis is stratified by gender, 4 calendar periods and smoking status which gives me the proportions within the ...
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117 views

How calculate Gini coefficient (unbiased) and Lorenz Curve with stratified sample?

I'm working with a stratified sample by minimum variance method with 3 levels that becomes at 1176 stratum. The sample comes from finite population of income taxes data. I'm looking for how calculate ...
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1answer
64 views

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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1answer
8k views

How to stratify a dataset to keep groups of data together in Python?

I have a dataset I want to use for machine learning that looks something like this: ...
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1answer
403 views

Horvitz-Thompson variance estimation when estimating across strata

I have a sample of Business units, which has been stratified according to two stratification variables (Revenue class and field of Business acitivity). Within the strata, Units were sampled according ...
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1answer
101 views

Combined analysis?

We have performed analyses by dividing the participants into 6 groups. The attribution of the groups was based on two variables: the Body Mass Index (BMI) and Metabolic syndrome (MetS): if BMI<25 ...
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441 views

Election fraud detection: the statistics of Quick Count

I’m reading the book Quick Count and Election Observation (chapter 5). I’m interested in understanding the statistics used in Quick Counts. Quick Counts is a methodology for verifying official ...
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1answer
125 views

calculate properly statistical moments with stratified sample data

I have problems of how to calculate properly the third and fourth order moments: my data is a stratified sampling with three strata. The goal for me is to make a descriptive analysis: mean, variance, ...
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86 views

How to calculate a sample size in the case of a stratified 3 degrees sample design ?

I am trying to calculate the sample size (and the repartition between PSUs and SSUs) needed to obtain an estimation of a proportion (that I assume to de around 50%) with a 0.05 standard error in the ...
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229 views

Confidence intervals on weighted proportions

I am conducting a survey that will identify and quantify the extent to which businesses in a certain industry reuse, recycle and dispose of their waste. I am trying to figure out how I would be able ...
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383 views

Stratified sampling when creating a test/training set

I am creating a dataset that I am going to use as the training/test sets for a supervised classification problem. The problem is to identify quotations in a large corpus. I have randomly sampled the ...
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49 views

Is there a method of stratum selection based on minimising variance within strata?

I have a population of about 7200 businesses from which to sample 2100 for a survey. The sample is to be stratified, but I have no information whatsoever on the usual way to stratify this population, ...
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208 views

What is the procedure to choose which strata to use if you have multiple strata available?

I have multiple characteristics of a population available (gender, age, place), and I have the answer for each individual for a particular yes-no question available done previously. For example, here ...
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1answer
2k views

Neyman Allocation Standard Deviation for Proportions

I am currently working towards the Royal Statistical Society's Higher Diploma and have run across a strange result in one of their sample papers that I can't work out - wonder if anyone can help me. ...
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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 ...