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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24 views

Logistic regression: age covariate within age group strata

I am using logistic regression to calculate the OR of falling using certain predictors (e.g. strength), age is also a confounder. The effect of age appears linear - risk of falling incrementally ...
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How to make a stratification in a penalized logistic model with the penalized function?

I use the R package "penalized" and I want to fit a stratified penalized logistic regression model. In the package vignettes, I found: It is possible to include an offset term in the model. ...
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Base weights/Relative weights when sampling strata change

I have survey responses from a survey where the sampling plan was stratification with sampling rates proportional to the square root of the number of households. The plan created 12 strata, and the ...
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Stratified sampling - use of proxy variable

For splitting of the data into train/test/val I use stratified sampling. Is it appropriate to define strata using information extracted from the dataset? E.g. use machine-learning to model proxy ...
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44 views

Data split using model's error

For splitting of the data into train/test/val I use stratified sampling. Then I confirm that metadata distributions represent the original dataset well enough. I want to start considering error of the ...
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Jensen-Shannon Distance between two Stratified Sampled Tabular Datasets

I have 100 unique joint probability mass functions with a dataset noting the prevalence of instances from each joint pmf, like this: The total amount of instances in this case would be 16,073. Each ...
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65 views

Precision and recall estimated with stratified sampling

I have a population including rare events (let's call them "event A") and I want to evaluate the precision and recall of a new algorithm to detect the rare events. In the actual population, ...
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11 views

Using stratified k-fold cross validation for time series model selection

This thread talks about the use of k-fold cross-validation for time series model selection where using the rolling basis approach is recommended, but I'm wondering how one would adapt this to a ...
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61 views

Sample Size determination at coutry level or states levels

A country is stratified into states. A researchers wants to carry out a survey with a main requirement of state level data representation. I wonder if sample size should be determine using country ...
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Stratified Sampling from a population according to given weights

I have a population and i want to take a sample from it in order to examine a mean of a characteristic (say $p$ the probability of having an infringment).My population is 13996 and are divided into 7 ...
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Balanced Allocation of Subjects to Base/Target

Lets say I'm conducting an experiment / AB test on a very volatile measure. I have a set of good estimators for this measure, which is known to me at the moment I need to assign each subject/...
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Stratified sampling ratio with srswor

The variable X under study have rectangular distribution with interval (a, a+ d ) the interval is divided into k equal subintervals which form k equal strata of equals sizes . From each stratum ...
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Is sampling by even/odd serial numbers a simple random sample?

I'm working on a project where each member of the population has a serial number. Each serial number is issued sequentially, so smaller serial numbers reflect older records. I'm drawing a sample of ...
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Random draw and fraction of each class is arbitrary [closed]

I am working on a dataset with binary outcome variable $\{0,1\}$. The data provider said samples are drawn randomly from the population while the sample proportion of outcome $0$ is arbitrarily set. ...
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87 views

Bootstrap to control for confounding variable - sample size

I am interested in the effect of dichotomous variable A on several scores for a sample size of N = 469 (observational data). Most scores have a non-normal, asymetrical distribution. Here's the ...
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What interval should I use to describe the variation caused by the randomness in stratified random sampling?

I have a population with n individuals. I decide that stratified random sampling is appropriate and I randomly survey a single individual in each strata, ultimately surveying ...
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validation and test set definition for active learing with rare classes

Context I've got an active learning problem with an event rate of about 1%. The data is a panel, individuals over time. We have a proxy label that is highly correlated with the true label within ...
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What is the best cross-validation scheme for churn prediction with time varying data per client?

I am looking for the best cross-validation strategy to test the performance of a churn prediction machine learning model (classification). The model predicts if a client is going to churn in the next ...
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Comparing two sample proportions where one proportion (p1) is a stratified sample and the other is a convenience sample taken from p1 (p2)

I have taken a stratified sample of vaccination clinics from a population in the US based on a categorization of A, B, C. I have sampled 2k clinics from A, 1k from B, and 1k from C. I am interested in ...
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Linear regression in very unbalanced data

I hope you can help me with this question. I have a dataset with several classes (around 25) and they are very unbalanced. Some classes have thousands of subjects, others hundreds, and others just a ...
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54 views

Stratification of Random Walk Jumps in Metropolis-Hastings

I aim to achieve variance reduction in Random Walk Metropolis Hastings algorithm by introducing stratification to the random walk jumps. What I have tried is to make use of Latin Hypercube Sampling in ...
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Stratification McNemar Test in R

I have categorical data before and after a condition (paired data) about preferences (yes/no) and I have other variables such as sociodemographic values (sex, ethnicity, etc). What I need to know if ...
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1answer
155 views

Am I correct in my understanding adjustment for covariate vs. stratyfing by it in the Cox regression?

I'm trying to understand the difference in a Cox model between adding a single categorical covariate like sex = {male, female} and doing stratification by it. I'm not saying about such trivial thing ...
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Why use a stratified log-rank test if we balance over strata anyway?

When comparing survival data over time, we can use the log-rank test. An extension of this is the stratified log-rank test, which adjusts for variables. Let's say we wanted to adjust for the effect of ...
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If I want to control for race in SEM, should I include race in the model, or should I run the model multiple times with 1 race category at a time?

I am running a SEM model. There is 1 independent variable, 1 mediator, and 2 dependent variables. All variables are continuous. I want to control for race (White, Black, Latino). To control for race, ...
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In a stratified RCT, should strata be combined if a too small sample size is attained in randomization?

My question refers to a situation where the number of participants in some strata is unexpectedly low. Should randomization proceed in the same way as declared in the Protocol, i.e. by performing ...
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Relative increase of variance for stratified simple random sample

My attempts: I know that for a stratified simple random sample, the variance of $\hat{t}_{y,st}$ is $V_p(\hat{t}_{y,st})= \sum_{h=1}^L N_h^2(1-\frac{n_h}{N_h})\frac{S_h^2}{n_h}$ where $S_h^2$ is the ...
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Is there a need to account for confounders if crude association is not significant?

Background: Swallowing exercises are prescribed to head and neck cancer patients during radiotherapy to prevent swallowing impairment Aim: Determine impact of swallowing exercise compliance on ...
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How to weight samples in a subsample of a stratified sample?

Suppose I'm first interested in computing the percentage of people in a certain town with brown eyes. However, due to some constraints I end up with the following stratified sampling set up: $$N = ...
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Computing estimates for segments of a sample

Suppose I want to estimate the average body weight of people in a population. I use a stratified sample of 50% men and 50% women and compute the desired metric. Next, I want to compute the average ...
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Post-stratification: What are the possibilities if your data has too many factor levels to run?

The example below is a simplified version of my actual problem and data. I have a sample of n=2000 observations of individuals surveyed throughout a country in a certain year. So my actual data is not ...
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49 views

How to do augmentation and k-fold cross validation?

I am solving one NLP problem which by default gave me train and test data. Test data has no labels while train has. Now I split train dataset into train(I will call this as updated train dataset) data ...
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Would very small stratum be a problem for ANCOVA model?

I know that for logistic regression, if you get an empty cell, the model may not run at all. How about continuous outcome? If one of the categorical predictors has very small stratum, would there be a ...
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Determine stratified sample size $n$ with confidence level 95%, if required $SE $ of the estimated mean is given

I need to calculate sample size $n$, so that $SE$ of the mean would be 4 points. There are $55$ units in total in the $I$ group. $N_2 = 80$ in the $II$ group and $N_3=65$ in the $III$ group. The ...
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How to show that $n_h $ is proportional to $\left(\frac{W_h^2S_h^2}{t_h}\right)^{\frac{3}{2}}$?

If cost function is given in the form $C = c_0 + \sum t_h\sqrt{n_h} $, where $c_0$ and $t_h$ are known ($t_h$ - transport costs to survey one element in a particular strata). Show that minimising $D(\...
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How to calculate and compare ML models Recall estimators from stratified sample?

Let's say that I have 2 machine learning models for a disease (binary) classification task. I would like to estimate Recall for both models and compare it (show statistically that for example Recall ...
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Confidence Interval around a single strata's proportion in a stratified random sample?

I am conducting a stratified random sample of properties in 10 cities of a binary attribute (has fence yes or no). This is using remote sensing so no response rate, it's me inspecting images of ...
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1answer
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Stratified shuffle for normally distributed target variable

When splitting data for a classification problem one is advised to use stratified shuffling in case the target variable is skewed toward a certain class. Indeed, Sklearn has a function for that. ...
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What is the optimal sampling split for stratified sampling?

Suppose we have a population split into two strata of interest and we want to estimate the mean of some quantity of interest pertaining to the population. Denote the quantities of interest for the ...
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Conducting a Stratified Random Sample (Statewide Poll)

I am interested (in theory) in conducting a stratified random sample of $n$ registered voters from a state which has 150 counties. If I make all 150 counties my strata, must I conduct a random sample (...
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How to determine sample weights, when the prevalence in the population is based on percentages

The central question is: How to do I determine the weights, when prevalence in the population is expressed as percentages? I have posted this related question on Stack Overflow: According to the ...
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1answer
60 views

How to group countries with similar age distributions?

How can I group the world's 200-odd countries into (say) ten groups, with each group's countries having 'similar' age distributions? I want to compare COVID-19 fatality rates across countries. But the ...
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Can I read into the coeff or the effect size of independent variables in a mixed-effects logistic regression model if I did stratified sampling?

I am building a mixed-effects logistic regression model. I want to understand the impact of certain predictors. I am reading into the coefficients and the effect size (wald's statistic). One of the ...
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118 views

Determine sample size for each cluster

Suppose I have a large population and I want to test if installing a new special light bulb can reduce energy consumption. Since I have a large population, I'll have people that usually consume high ...
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1answer
88 views

Creating stratified subsamples from a sample (repeated observations) - Post stratification

I have a random sample of individuals in a country (without knowing in which province they live). From this sample I want to make stratified random samples on the provincial level (let's assume there ...
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1answer
143 views

How is stratified sampling better than sampling equally from all classes while crossvalidating?

I can see that stratified sampling helps in maintaining the same class distribution in the training set as in the original dataset. However, my understanding is that ideally, the model should be ...
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crossvalidation "balancing" for regression problems

Classification problems can exhibit a strong label imbalance in the given dataset. This can be overcome by subsampling certain class weight attributed weights, which allow for balancing the label ...
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What is a non-random k-fold cross-validation that is not aimed at representativeness?

I am working on a project where my dataset is structured as follows: for each observation, I have a concept translated in five languages, and a measure of word concreteness. So something like: ...
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Ex-post grouping blocks, when analyzing blocked randomization experiment, to avoid $N_b=1$ blocks

In an experiment I conducted, randomization was stratified geographically and then blocked by the baseline outcome variable, $x$. That is, within each strata, $s$, I grouped observations into blocks, $...
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Proportional allocation vs Neyman Allocation [duplicate]

I am trying to figure out how to use both allocations for an assignment and I am having a hard time figuring it out. More importantly, can someone explain how to use proportional allocation to me by ...

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