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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448 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
77 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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68 views

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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350 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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128 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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54 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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1answer
66 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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1answer
528 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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2answers
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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0answers
429 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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1answer
156 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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1answer
40 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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1answer
176 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
115 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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1answer
48 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
171 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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1answer
213 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
326 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
603 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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0answers
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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528 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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195 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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433 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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1answer
474 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
13k 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
71 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
840 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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131 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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116 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
60 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
7k 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
375 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
99 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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431 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
120 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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0answers
82 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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0answers
223 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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367 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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0answers
42 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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201 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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1answer
1k views

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 ...
0
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1answer
867 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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1answer
583 views

K-fold in grid-search for linear svm C parameter giving same value?

So every time I do a GridSearchCV with KFold, stratified or not, I get the same accuracy score and STDev for values of C=1,C=10, and C=100. I then did a special ...
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1answer
137 views

Can interactions save power in a regression (vs. stratification)?

I have data with about 700 observations total. There are 9 subgroups in my sample with sizes ranging from 54-96. I want to use linear regression to explore how 8 independent variables might predict ...
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1answer
119 views

Downsides of stratified randomization in experimental design

When sample sizes are too small to trust that the usual asymptotics will guarantee good balance across experimental groups on known confounders, a common approach is stratified or blocked ...
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1answer
633 views

How to avoid overfitting in stratified k-fold cross validation methods for classification?

I'm using stratified 10-fold CV on my data set that is imbalanced. I've read in articles that this method is useful for such data set. But I'm not sure if I'm using this method as well. In each fold, ...
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168 views

dataset shift and adjustment in glmnet

I have two sets of data A and F; In each datasets, I have two types of data point, say, 0 and 1 and the goal is to make a classifier. One strategy is training/fitting the model, using one dataset, ...