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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186 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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437 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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78 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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632 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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460 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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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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45 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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58 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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33 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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226 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
227 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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252 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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117 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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290 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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167 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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37 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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35 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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142 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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56 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
177 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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570 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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199 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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463 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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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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85 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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369 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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203 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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171 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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367 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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56 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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33 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
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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1answer
678 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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1answer
30 views

Stratified Sampling on Random Forest

I am working on a project to detect crops from satellite images by prediction. To do so, I use Random Forest model. I discussed with some people about whether to give sample weights on each tree in ...
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How fine is the finest cluster level in a sample with individual data?

When using software to estimate the variance or standard error of statistics calculated from complex survey samples with clustering and stratification, if the sample contains data on individuals, is ...
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2answers
16 views

k-fold CV-scheme stratifying response and considering groups

I have the following small dataset (n~140): 1-8 samples per patient A small fraction of samples belonging to the negative class (no tumor), ~ 10-20% A larger fraction of samples belonging to the ...
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How to do post-stratification weighting in sampled groups with low or zero cell populations?

Let's say you received data from a sample. You don't have information on the sample design, but you have population data so you want to employ post-stratification weights to better align the sample ...
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Multiple Imputation with categorical variable for treatment: Do I have to impute stratified by treatment?

I want to impute data for a clinical trial with four treatments and analyze the data to determine if there is a treatment effect. Normally I would perform the imputation stratified by treatment so ...
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3 views

Stratified Log Rank Test with Unequally Sized Strata

If I perform a stratified log rank test in a situation with many strata (currently I have 8), in 6 of the 8 there are very small numbers (i.e., 1 or 2%), but the other strata are fairly balanced, how ...
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17 views

Stratification or minimisation…Necessary with sample sizes exceeding 250?

I was having a discussion with a statistician who developed a simple software package to do participant group allocation using the minimisation technique. In this discussion the person mentioned that ...
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21 views

compute AUC and statistical testing of stratified data

I have a dataset where samples are stratified in groups. That is, there are N samples per examination, and M examinations per subject. I would like to account for this when estimating the ...
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9 views

Difference between Confounding and Effect Modifier

I am searching everywhere about the differences between Confounding and Effect modifier, but not able to find it. Kindly help me in this. Can you please answer using examples rather than definitions.
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35 views

Should stratified cross-validation be used in a regression context?

After a number of Google searches and looking at various stack posts, I cannot find much information or discussion about using stratified cross-validation in regression context. I am modeling forest ...