Skip to main content

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.

Filter by
Sorted by
Tagged with
2 votes
1 answer
42 views

Should I normalise a sample drawn from a skewed population?

I am interested in the effect of the number of inhabitants of political entities on certain political behaviours within these entities. It happens that the number of inhabitants is not evenly ...
CNiessen's user avatar
0 votes
1 answer
18 views

How should stratification factors be accounted for in analysis?

In the context of a clinical trial with time-to-event primary endpoint, if stratified randomization is used for subject enrollment, how should the stratification factors be accounted for in the ...
Will_Zhang's user avatar
4 votes
1 answer
148 views

Interpretation of R output for stratified cox-ph model

For the following model: model <- coxph(formula = Surv(time, status) ~ treatment * sex + strata(sex), data = data) this is (part of) the model summary in R: ...
user412691's user avatar
1 vote
1 answer
26 views

a few questions on stratified analysis

If one of the 3 stratification factor from IWRS has data errors, should we replace it with CRF collected baseline values? Will this break the balance of the strata blocks? For non ITT population, say,...
ziweiguan's user avatar
  • 519
1 vote
2 answers
113 views

Adjusting for stratification variables

In clinical trials, stratification may be used to ensure balance of treatments across covariates. According to guidance documents (e.g. EMA/CHMP/295050/2013) stratification variables should usually be ...
user7064's user avatar
  • 2,207
3 votes
1 answer
146 views

When and how of stratification?

I understand stratification at a novice level. For example, if we want to condition on gender in post experimentation inference, we might stratify or block on gender. As I understand it, we take each ...
jbuddy_13's user avatar
  • 3,382
1 vote
0 answers
33 views

Stratified sampling across several variables individually

I am interested stratified sampling for the purposes of cluster validation. The purpose is to perform cluster analysis in a subset of the data and check to see if the precise distribution of variables ...
pvelayudhan's user avatar
1 vote
0 answers
48 views

Random permuted block sizes in a randomised clinical trial

What is the best way to choose the block sizes in a randomised clinical trial? Randomisation for an ongoing trial is stratified by site (2 sites) and gender (m/f) for 4 strata - it uses random ...
Megan Moreton's user avatar
0 votes
0 answers
6 views

Studying more than one sampling unit in a single randomization

So we have a list of organizations that dedicate themselves to a certain social service. Our goal is to ask both laborers and customers an overlapping(but not fully) set of questions for each one of ...
Vacoiide's user avatar
3 votes
1 answer
26 views

Cluster sample or stratified random sample?

I've recently come across this problem in my textbook: To gather information about the validity of a new standardized test for high school juniors across the United States, a random sample of 20 high ...
wyatt400's user avatar
  • 105
0 votes
0 answers
13 views

Do replicate weight, when the are available, supersede all the design-based procedures and analysis?

If the agency that conducted a survey and releases micro data at the individual or household level also supplies replicate weights for that sample, do these weights completely supercede any need or ...
andrewH's user avatar
  • 3,157
2 votes
1 answer
49 views

Confidence intervals around treatment effect in stratified experiment

Suppose you conduct an experiment, where a population is randomized and treatment is given to the treatment group and you are interested in covariates (stratification has been employed) and their ...
jbuddy_13's user avatar
  • 3,382
0 votes
1 answer
17 views

Relative importance of equal sample size vs equal sample density

I am conducting a vegetation study of the effects of prescribed fire. I have an experimental area that will be burned and a control area that will not be burned. The experimental area has three types ...
ia200's user avatar
  • 123
0 votes
0 answers
19 views

How to account for population stratification in Fisher test?

When performing a logistic regression this can be done by adding covariates. How could I do the same for a Fisher test?
Caterina's user avatar
  • 229
1 vote
0 answers
19 views

Power analysis for Blocked/Stratified design?

I'm curious how power analysis can be conducted when the scientist is stratifying on one or more variables? I came across this approach but it went over my head. Ideally, the answer would not be "...
jbuddy_13's user avatar
  • 3,382
0 votes
0 answers
24 views

Stratified boostrap for stratified experiment

I'm running an AB test where I split customers into A and B by stratifiying on the levels of a variable X. I collect data like this: ...
David Masip's user avatar
0 votes
0 answers
16 views

Consider an example with two strata for n=300. Suppose optimum allocation is sample sizes of 200 and 100 in the two strata. The approx sample sizes

Consider an example with two strata for n=300. Suppose the optimum allocation requires sample sizes of 200 and 100 in the two strata. The approximate sample sizes actually used are 180 and 120, ...
Gadin Naidu's user avatar
0 votes
2 answers
120 views

What's the magic of randomization? [closed]

I've read that one can perform A/B tests & effect size inference given that a population was randomly sampled and allocated to A & B groups. You simply give the treatment to group B and the ...
jbuddy_13's user avatar
  • 3,382
1 vote
0 answers
15 views

How can I estimate ATT for each stratum [closed]

the following code if for estimating ATT, my question is :if I want to estimate ATT for each stratum,can I use this code and how can I change it to give me ATT for each stratum? ...
alireza beheshty's user avatar
2 votes
1 answer
100 views

Should I use strata(), cluster() or frailty() to account for center specific characteristic in a time-varying analysis

The research question revolves around whether a time-varying intervention at a center enhances the transplantation hazard per person. I have patient-level data and I need to account for the center ...
Claudio Bravo's user avatar
0 votes
0 answers
9 views

Static risk prediction models and years-to-live stratification

A known paradox is the fact that although the absolute risk for developing a disease may rise with age, the conditional probability for every person to develop a disease, given that he hasn't ...
zvika segal's user avatar
8 votes
2 answers
289 views

When to use fixed effects or multi level models in regression?

Suppose you run an experiment where the treatment is Gatorade and the outcome is one-mile runtime. You’ve stratified on variables such as sex, height and weight so they’re well randomized and have no ...
jbuddy_13's user avatar
  • 3,382
1 vote
1 answer
227 views

In SAS what is the difference of including treatment variable in model and using the strata statement for treatment variable?

Im building a Cox Regression in SAS. My code looks like this: ...
Jam.Wil's user avatar
  • 77
0 votes
1 answer
109 views

Stratified SRS vs. probability-proportional-to-size (PPS) sampling - what's the difference?

If my understanding is correct, the key difference is that: In stratified SRS you intentionally draw $N_h$ samples from each of your $k$ strata ($h = 1...k$, $\sum_{1}^{k}{N_h} = N$) and are ...
k13's user avatar
  • 47
0 votes
0 answers
39 views

Regression on a Stratified Sample [duplicate]

I am doing some regression analysis on a stratified sample where the stratification variable is the dependent variable. Do I need to adjust the regression or the results to account for the ...
aabceh's user avatar
  • 1
0 votes
0 answers
13 views

Validation of a stratified randomization plan

In my team, we are conducting clinical trials using stratified block randomization with random block size. Depending on the user, the randomization list will be generated using custom SAS macros or R ...
Dan Chaltiel's user avatar
  • 1,440
0 votes
1 answer
42 views

Understanding stratified approximate randomization test

I have been looking at a code base that can calculate evaluation metrics. It implements bootstrap resampling to calculate confidence intervals, and also uses stratified approximate randomization for ...
Bram Vanroy's user avatar
2 votes
1 answer
604 views

Stratified-Extended Cox regression modeling to deal with survival data with time-varying covariates

I'm working on Cox regression in my PhD research and I would like to know some references about applying the stratified-extended cox regression model on a real life data. I'm interested about ...
Youcef Bouzir's user avatar
1 vote
0 answers
27 views

How should we stratify the space for Metropolis-Hastings?

Say I'm running Metropolis-Hastings with target density $p$. What I would like to do is divide the space $E$, on which $p$ is defined, into a disjoint union $E=\bigcup_iE_i$ and run a separate ...
0xbadf00d's user avatar
  • 303
1 vote
1 answer
72 views

How to deal with survival analysis when censoring time depends on a covariate

I'm performing survival analysis on time to drop out of a certain program. However, the censoring of each case depends heavily on the length of the program. For example, some programs only last 3 ...
Dalliance's user avatar
2 votes
3 answers
253 views

What is "information leak from test to train" ? Is stratification by target a leak?

It's common practice to do procedures such as standardization and even missing value imputation (commonly based on some means) after train/test split - otherwise it is treated as information leak from ...
Ars ML's user avatar
  • 31
0 votes
0 answers
139 views

Stratified sampling for household dataset. Multiple targets or single target?

I am new in stratified sampling. I have a regression task to analyse the relationship between income, household size and expenditure, using python. Both income and expenditure are continuous variables,...
Lu Cas's user avatar
  • 11
-1 votes
1 answer
72 views

Which of the variables appear to be effect modifiers. When stratifying by each variable, which seem to indicate the presence of interaction?

The following graph displays five pairs of stratified odds ratios (not from the same study) with 95% confidence intervals. For this plot, assume the confidence intervals indicate whether the stratum-...
phoebehalliwell's user avatar
1 vote
0 answers
36 views

Relative Error when using an erroneous neyman allocation

I'm having a lot of issues trying to derive an equation for the relative error in the following problem. Someone has used the following incorrect formula to perform Neyman allocation $n_{h,e}=n\frac{...
Jack Gorman's user avatar
1 vote
1 answer
454 views

Is Neyman allocation sampling the best approach?

I have a data set of the 2020 value of 15,000 unique objects. The value is right skewed. I have to draw a sample of 500 unique objects based on the 2020 value (range = $1-40,000). The present value of ...
burnt_pianos's user avatar
1 vote
0 answers
11 views

Disproportionate stratified sampling that follows proportional trend?

I'm conducting a study across four counties to determine which of four different methods is most effective in detecting nutria. 60 sites will be randomly selected within a 5-meter buffer of any open ...
dwhip's user avatar
  • 11
0 votes
0 answers
36 views

Is it appropriate to pre-stratify and post-stratify along different delineations of the same variables in a single survey?

I am working in the context of opt-in, web-based surveys. Often the desire is for accurate population estimates, and often at a country-wide level. The standard approach at this organization is to ...
spathartic's user avatar
1 vote
0 answers
21 views

How can I show probability of selection change when adding stratification to a survey design

I have a survey that uses a stratified sampling approach with optimal allocation. The team conducting the survey has asked that we make two changes: Subdivide one of the strata into smaller pieces. ...
B. Bogart's user avatar
  • 123
1 vote
1 answer
331 views

Why can stratified sampling to testing/training sets on strata that contain less than 10% of the entire dataset be statistically risky?

I'm trying to split my data into a testing and a training set. There are lots of variables that I want to ensure are well represented in both the training and testing sets (say, 15 covariates). But ...
Aegis's user avatar
  • 183
1 vote
1 answer
89 views

Are stratified variables still significant?

...
Antonio's user avatar
  • 673
0 votes
0 answers
390 views

Grouped stratified train-val-test split for a multilabel dataset

I was wondering if there is a fast heuristic algorithm for performing grouped stratified dataset split on a multilabel dataset. Question originally posted on Data Science stackexcahnge here. ...
jasperhyp's user avatar
0 votes
1 answer
34 views

Stratified cox reg analysis

I am trying to make a stratified cox reg analysis in R studio, where I want to see the differences in exposure to MT divided by gender. I used the following code: ...
Sarah's user avatar
  • 1
2 votes
0 answers
64 views

pre-stratification(blocking) vs post-stratification

$Q:$ When should I consider pre-stratification(blocking) vs post-stratification? From experiments, I would certainly consider pre-stratification but post-stratification seems to homogenize the sample ...
user45765's user avatar
  • 1,445
0 votes
0 answers
97 views

Strata Sample Sizes and Stratified Sampling

I am trying to conduct a research study on the local population of homeless individuals in my county. But, before I can detail my study, it would be helpful to provide some context. Context: It is ...
Trent's user avatar
  • 101
0 votes
1 answer
167 views

How do you calculate the total sample size in stratified sampling?

I know that we can allocate observations from the total sample to each strata either using proportional allocation ($n_{h}/N_{h} = n/N$) or optimal allocation: $$n_{h} = \left [ \frac{\frac{N_{h}S_{h}}...
NoLifeKing's user avatar
1 vote
1 answer
809 views

Inconsistent handling of lonely PSUs in R's `survey` package?

There appears to be some inconsistent handling of lonely PSUs in R's survey package when calling svyglm on a subset of ...
Eric's user avatar
  • 13
0 votes
0 answers
19 views

Optimal sampling strategy when only marginal group sizes are known

I seems to me that this cannot be such an uncommon situation but I find I cannot come up with the answer myself and I also cannot come up with the correct search terms to find it, either here on Cross ...
Ishisht's user avatar
  • 227
2 votes
2 answers
131 views

Train test split based on statistics

I would like to know if there is a method of splitting that is not random but based on the distribution of the train and test data samples feauture values. Currently I am splitting randomly but ...
Birk's user avatar
  • 33
2 votes
1 answer
58 views

Age and sex standardised incidence rates

If I were to compute age-sex standardised incidence rates based on a simple random sample of a nationwide household survey on hearing loss. Noting that this a sample not the total population, so the ...
SarahJ's user avatar
  • 23
3 votes
1 answer
2k views

Computing standard errors when using stratified sampling

I am trying to understand the following formula for the standard error of the population mean as estimated through stratified sampling. On the CRAN site, the formula given is $$ S_{\bar{x}_{\textit{...
ted's user avatar
  • 741

1
2 3 4 5 6