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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23 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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20 views

How to perform inference on stratified sampling data

Let's say I'm studying a population of generic emergency calls to over the course of several months, and keeping track of the following independent variables: month (when the call happened) country (...
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135 views

Neyman allocation and proportional allocation

Suppose that a city has 90,000 dwelling units, of which 35.000 are houses, 45,000 are apartments, and 10,000 are condominiums. We want to estimate the overall proportion (p) of households in which ...
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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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10 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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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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11 views

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'...
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33 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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Estimating a population proportion and credible interval from a biased stratified sample

I am attempting to calculate a point estimate and the upper 95th percentile (one sided credible interval) for a defect rate (i.e. a population proportion) using the results of a biased stratified ...
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57 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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65 views

Determine sample size using reversed goodness of fit

I am asked to work on a specific problem in which I have to calculate certain expenditures for an industry, consisting of a population of about 400 companies. Although I already suggested to conduct a ...
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8 views

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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26 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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13 views

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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22 views

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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4 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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135 views

Interpreting hazard ratios in stratified models

I am unsure how to interpret hazard ratios from cox-proportional hazard models that include 1 or more stratified terms. For example, say I run a cox regression with treatment as a covariate and ...
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24 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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1answer
63 views

Odds ratio not between the two odds ratio of a stratified analysis

This is not the first time I have performed stratified analyses based on logistic regressions, but I have never before been confronted with this situation. When I test my relationship in the overall ...
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179 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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32 views

random vs. stratified Cox model

What is the difference in interpretation of the effect estimates in a Cox model stratified by sex vs. with a random statement for sex? Thanks.
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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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54 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 ...
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57 views

Nested CV with Stratified Kfold

I am using nested CV for model evaluation and my target variable has imbalanced classes. With Sklearn, I am using GridSearchCV and cross_val_score to perform the nested cross validation. Each takes ...
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8 views

Least square estimate for post-stratification sampling

I figured out via the normal linear regression method that Beta0 hat = ybar - Beta1 hat xbar. But I am not sure how to find out the least square estimate for Chat. Is anyone able to help me? Thanks!! ...
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63 views

Calculating sample size for a stratified random sample

I have a total population of 4,000 farmers, divided into three unique regions. Approximately 50% of the farmers live in Region A (N=2,000), 27% in Region B (N=1,080), and 23% in Region C (N=920). I am ...
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Stratified Sampling: Given required bound, calculated $n_h$ is bigger than $N_h$?

I'm dealing with a question that has given me a peculiar result and I would like someone's opinion on how to deal this: Say you have a population of $N=550$ objects: $N_1=75$ red and $N_2=475$ blue. ...
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17 views

Stratifying a multivariate dataset

I woul like to stratify a multivariate dataset in different stratas in such a way that the elements of each strata are similar. My idea is to have different groups whith the element within a group ...
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788 views

what's the difference between stratified sampling and matching?

I am trying to find a good technique to balance data in which the minority class is about 1% of the data. As I understood, the most common practice is matching. What is the difference, though, ...
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176 views

Fold size and stratified k-fold cross-validation dilemma

So, as far as I understand, all folds in k-fold cross-validation need to be the same size, or as close as possible. However, if one uses stratified cross-validation, each class should be represented ...
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141 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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163 views

Optimal multivariate binning where the cut-points must be the same for all observations

I have a large data set with many discrete and continuous variables. All the variables are present in every observation. I want to explain (the log of) one continuous variable using all the other ...
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178 views

Stratified cross validation with groups

I have a model for a binary classification problem that I want to cross validate. The data is divided into groups. Some groups contain samples in both classes, others only contain samples from one ...
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31 views

What methods exist for multi-output stratification (multi-label with different mutually exclusive label sets)?

To elaborate a bit: Methods do exist for single-output multi-label stratification (e.g., see scikit-multilearn). And there's a perfectly serviceable naive method for multi-class problems. The ...
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40 views

How to control for severe medical cases using survival analysis and Cox regression?

I have a longitudinal medical record dataset. My cohort is made up of patients with a particular disease. There are no members of this cohort without this disease. Disease indications are denoted by a ...
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Model to Impute strata data according to higher level data

I've got regional level data and I want to impute said data on a county level strata (smaller strata with respect to the regional strata). I know I can do that if I have a series of variables on the ...
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24 views

Sampling methods - Stratified Vs. Probability Proportionate to Size Cluster

India has 29 States, each of which is further sub-divided into smaller administrative Districts of varying size and population. I need to download micro (firm-level) data from each state, but I do not ...
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20 views

Regression model when stratified randomization is used

I have been going through articles on stratified randomization but I haven't seen one that elaborate regression function generated and also elaboration of strata effect on the outcome. I will ...
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213 views

Stratified Kfold splits by inputs instead of just being based on outputs

It's known that a stratified split can easily be done if there is a known imbalance in the output distribution (or output classes). Is it possible to do a stratified k-fold using the input ...
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35 views

What are the differences between Domain Estimation and Poststratification

Both of these two methods will firstly select a simple random sample without replacement and decide which groups these observations belong to and use ratio estimation to get quantities of interest. It ...
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756 views

Difference between Multistage Sampling and Stratified Random Sampling?

I know the question is a very elementary one, but I simply cannot understand the difference other than the fact that an SRS is a form of Multi-Stage Sampling. Can anyone provide a simple example(s) to ...
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56 views

what type of sample is this?

I have the folowing table: according to this example, there are 40 observations distributed over 10 stores and 4 weeks of the month. Objective: to make a sample of 90%, 80%, 75% and 50% of the 40 ...
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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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38 views

Cox model with a predictor variable within only one stratum

I'm investigating survival in a cancer patients cohort. The Cox model I'm using is stratified by stage and adjusted for several variables. I would like to add one variable RT (Radiotherapy) which is ...
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Prove significant effect of third variable on a correlation

So I was measuring correlations in Boxscores of basketball players in the NBA. 3PA DRB -0.205499 I was trying to find some interesting correlations. ...