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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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202 views

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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445 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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82 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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1answer
524 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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635 views

Stratified Cross-Validation with Collaborative Filtering

My dataset consists of binary preferences ($0$ or $1$) given by users on items like this: User-ID | Item-ID | Preference If a user has not given a preference to an item, then it is not in the ...
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65 views

Stratum on subset of data: drop if too small?

We have genotype data for ~20000 samples with 4 principal components and 10 strata - study centres. Formula for an example analysis would be: ...
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47 views

Can unintentional sample stratification be problematic?

An example of what I mean: I have a certain essay from all students at a university. I take a 1% random sample (not stratified) and run some time consuming computational analysis on each essay ...
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70 views

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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36 views

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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645 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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231 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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2answers
237 views

Why class stratified sampling is not compatible for naïve bayesian modeling, if sampling is used?

I read a book recently and it mentioned related to prior probability of naïve bayesian: "Since the probability of an outcome is calculated from the data set, it is important that the data set used ...
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257 views

Correlation with stratified data structure

I have a dataset with two stratas, the first level is called block, which represents the census block. the second level is two predetermined subgroups in each blocks, each subgroup contains several ...
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2k views

Calculating needed sample size for two stage stratified cluster sample

We want to carry out a survey to assess perceptions of quality and access to medical education of last year students. Based on our research, we have decided that a two stage stratified cluster sample ...
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122 views

How to calculate the number of samples necessary to represent a population distribution?

I guess this is similar to this one but not quite the same. Consider I have a distribution that represents a population (e.g., Uniform(0,1)). I separate this interval (0,1) into three equal parts (0-1/...
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295 views

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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302 views

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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9 views

Simulate confidence intervals for the absolute difference between two hazard ratios

I am examining the time to an (recurrent) event in response to different medications between men and women. I am adopting a 'within-individual' design whereby each person's time spent on- and off- the ...
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31 views

multilevel regression and poststratification mrp

I have some survey data. I want to calculate a regression with a stratified sample of this data. Because of the stratification, the sample size gets really small. Due to this, the standard error of ...
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177 views

Calculating a sample size based on the target width of a confidence interval with stratification

I am reviewing a sampling design devised by a colleague and completely fail to understand it, although I am not a novice in statistics (but not a huge expert either). The said colleague is no longer ...
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140 views

how to use boot package to do stratified bootstrapping?

Here's a toy data set that replicates my problem. I am interested in knowing the confidence intervals of an empirical distribution that is composed of the scores of each school at the proportion that ...
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43 views

Benefit of scaling survey design weights

In the european social survey the design weights are scaled to the sample size (see quote and source): As with the design weights also the post-stratification weights are scaled to the sample size, ...
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43 views

Sampling - optimal allocation for quantiles?

Say we have variable with a typical heavy tailed distribution following the Pareto principle. We divide the population into two strata (following the 80 / 20 rule) and use a stratified sampling design ...
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17 views

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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159 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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62 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
193 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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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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203 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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665 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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118 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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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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386 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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210 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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173 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, ...
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77 views

What does it mean if the ROC scores are quite different when using the Stratified K fold with and without shuffling?

I'm currently building a random forest classification and trying to measure the model performance by the [mean ROC area]. With the same data set: When I use cross_validation.StratifiedKFold(y, ...
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374 views

Stratified random sampling and its distribution

I'm learning stratified random sampling and I'm having hard time to solve this problem. consider the following population of six units: ...
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44 views

Accounting for noncoverage in survey

[I'm a stats noob, so please correct if I am going wrong somewhere!] We run a survey of our customers based on certain events or touchpoints. The responses vary significantly by these touchpoints, so ...
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57 views

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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34 views

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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59 views

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.)...
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1answer
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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1answer
709 views

Post stratification weights and the survey package in R

I have survey data that needs to be weighted, and to help me with this task, I have access to the full joint distributions of the variables I want to use. As I understand it, I should use the ...
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22 views

Should I use stratify parameter for scikit-learn train_test_split while dealing with highly unbalanced dataset?

I have a dataset with over 200000 records. Only 400 of are positive, which makes the data highly unbalanced. I cannot collect more data. At first I trained a decision tree. I used StratifiedKFold and ...
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5 views

Experiment design: what's the difference between diff in diff and post-stratification?

what's the difference between diff in diff and post-stratification? When should we use diff in diff and when should we use post_stratification quasi experiment design?
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18 views

Variance of estimator of stratified sampling

Consider a stratified design composed of $H$ strata of size $N_h$, $h = 1, . . . ,H$. We want to estimate the population mean $μ_y$ of the characteristic $y$. Let $μ_{x,h}$ $h = 1, . . . ,H$ be ...
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21 views

Stratification of sample data is lowering my accuracy?

So I've got this trainingset, it has a bunch of stuff yada yada.. Main point is that there are two target variables that only occur once in the dataset. This means I can't stratify when sampling, I ...
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21 views

Is doing oversampling on train set and undersampling on test set correct?

I have an imbalanced dataset (95% in class 0 and 5% in class 1) and I am using machine learning for classification. The AUC(Area under ROC curve) was high (about 0.86) but AUPRC(Area under precision-...
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Interaction results in two datasets are concordant, but stratified analyses are not

Let's suppose I want to explore the relationship between a variable (SNP, {0,1,2}) and a disease outcome (D, continuous value such as blood pressure), knowing that this is different in two groups, let'...