Questions tagged [observational-study]
An observational study involves purely observing the state of the world without manipulating it.
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How can mahalanobis and chi2-test be used to determine of an observation is acceptable?
Assume that you have a model
$$\dot x = Ax + Bu$$
$$y = Cx$$
And this model is SISO. Single input and single output. You got the mission to determine of an observation is acceptable for the kalman ...
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Bias in survival analysis: nice summary of all the different types and remedies
I am quite new to the field of survival analysis and am getting lost and confused with all the different types of bias that can occur, particularly in observational studies. For example, it appears ...
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Best Approach to Detecting Breakpoints in Continuous Treatment-Outcome Relationship?
I am currently conducting research to understand the relationship between a continuous treatment variable and a continuous outcome variable. To mitigate confounding and selection bias, I am employing ...
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Sufficient Sample Size for Three-way Interaction from Observational Data (2x2xContinuous)
I'm wondering how one determines the sample size needed to sufficiently analyze a three-way 2x2xcontinuous (logistic) regression interaction using observational data (association study)? Any ...
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Adjust for loss of follow up
I have a dataset containing 50,000 observations of individuals undergoing drug treatment in Chile from 2015 to 2019. I aim to examine whether polydrug use (intake of more than one substance at the ...
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How can I control for confounding sociodemographic variables, in a correlational study with two IV's?
I want to control for the effects of confounds in an observational study (using self-report questionnaires), however, I do not want to imply a causal relationship between my two constructs. Therefore, ...
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Confounding variables are nested with treatment, not able to be measured, how to address the influence from confounding factors?
We gathered driving data from two cohorts of drivers belonging to the same age group. The first cohort, Group A, utilized System A (treatment group), whereas Group B drove vehicles without this system ...
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Effects of multiple non-independent treatments
I need to run an analysis of efficiency of automated recommendations for call-centre agents on how to handle customer support tickets. It works like that:
A ticket get 0, 1 or more recommendations ...
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Conjunctive testing or not in retrospective study?
I have a device that can estimate 2 continuous, independent quantities A and B of its users.
There is an accepted criterion for "accuracy" for each quantity A and B.
Let's say I want to ...
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How should control candidates be decided for causal inference?
I’m getting a bit confused about who to include in the control and treatment pools and would appreciate the help. I need to estimate the effect of treatment where 100% of the population was assigned a ...
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How to estimate the effect of treatment duration on survival outcomes
I'm reading the paper "How to estimate the effect of treatment duration on survival outcomes using observational data"(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6889975/), and it states ...
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Why is covariate balance fundamental for causal inference in observational data but unnecessary in experimental data?
The observational case
For observational data, Hernán & Robins (2023, p. 49) state:
In the absence of marginal randomization, [computing the average causal effect in the entire population] ...
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Is this a breach of the consistency principle in causal inference?
My understanding of the consistency principle is that the observed outcome is equal to the potential outcome. i.e. let T = treatment, if T=1 then then the Observed outcome (Y) is equal to the ...
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How to account for immortal time bias in retrospective longitudinal studies from covariates during a baseline period?
I would appreciate your expertise. Firstly, I am not a statistician, so I kindly ask you as a statistician. The problem I am facing:
I am conducting a retrospective longitudinal analysis of patient ...
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Comparing treatment effects across groups
I created two donation campaigns, one loss framed (N:1993) and one gained framed (N:1989) I understood donations are usually veeeery low and the sample was a lot smaller than previously expected, so ...
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How to deal with patients falling out of the study more frequent in one treatment arm
I'm doing a retrospective comparison of two treatments (A and B) for eye disease. Both procedures have the same most common side effect (dependent variable) but their indications differ slightly ...
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Selecting correct study design and statistical analysis for my project
I am analyzing risk factors associated with surgical site infections where we want to have a 3:1 case-control study. Other than some brief lectures in my classes, the only thing we were taught about ...
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Why is the fully-symmetric bidirectional case-crossover design biased and the semi-symmetric design not when there are time-trends in the exposure?
I am trying to understand why the fully-symmetric bidirectional case-crossover design is biased when there are time trends in the exposure and why the semi-symmetric design is not biased?
I have tried ...
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Dealing With Immortal Time Bias in Observational Studies
I have an observational cohort of patients with underlying pulmonary disease. The cohort is derived from multiple centers across the USA. My scientific question is whether or not there is an effect of ...
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Observation in Quantile Regression
i have 30 observations of yearly data and i try to do quantile but results is all of my variables is not significant. im wondering if we can use quantile regression on yearly data? or is there any ...
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Can age ever be confounded if it is the independent variable in an observational study?
This is a follow-up to my previous question: "Basic understanding of control variables in observational studies"
I have understood the answer, but am still trying to figure out what I think ...
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What does look back mean observational studies?
Consider I am doing observational study either case control or cohort in either of the following cases.
Case. 1 Suppose I found enrollment/rate of population with disease is too low where disease ...
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How to adjust retrospective-observational survival times to account for immortal time bias?
I would be very grateful for a gentle sanity check on adjusting survival times in my comparison groups. The scenario: I am using Cox regression to calculate HR risks over some covariates of interest.
...
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Sample size calculation for non-inferiority prospective observational study with paired nominal data?
I'm doing a diagnostic observational study, where doctors in two different fields (emergency physicians vs radiologists) try to diagnose same patient (paired sample). The question we are trying to ...
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Is having multiple events with smaller successes better than having fewer events with a greater success if the success rate of each event is the same?
The best way I can explain my question is through an example. Let’s say I have two options. For option one, there is one hat with 10 pieces of paper. 8 pieces are green and 2 pieces are red. At the ...
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MatchIt Exact Matching without replacement (1:1)
I am trying to use the MatchIt package to conduct exact matching on several categorical variables (sex, zipcode and an eligibility group code). After matching I want to have the same number of treated ...
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Advice on study design involving longitudinal clusters and measurements
I'm conducting an analysis on several hundred thousand individuals to understand if there are longitudinal differences in an outcome across clusters of the individuals. My outcome is healthcare cost (...
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Wilcoxon signed rank for matched cohort study
I am hoping someone can help me with figuring out something I came across in this article ((https://support.sas.com/resources/papers/proceedings/proceedings/sugi29/165-29.pdf). On page 5 the authors ...
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test for difference between matched pairs in 1:1 matched study
Background: I have a retrospective study (registry) that contains data on people with kidney transplant. Among these patients, we have a very small number of people with a specific genetic disease (n=...
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The correct treatment of censorship and observation periods in survival analysis using longitudinal observational data
I have longitudinal retrospective data and want to perform Cox proportional hazards regression. Still, I would be extremely grateful if the CrossValidated community could sanity-check my understanding ...
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Sensitivity Analysis: Conceptual differences between "competing risks" in RCT and immortal time bias in longitudinal retrospective observation data
I'm reading a review-methodology article on Sensitivity Analysis in Randomized Controlled Trials (RCT): https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-13-92
Section (page 7 of ...
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Possible to have independent observations without random sampling?
Is some form of random sampling required for observations to meet the "independence" assumption of various types of regression analysis and hypothesis testing?
My data (fish counts, without ...
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Difference of baseline data between groups NOT significant on pre-matching [duplicate]
In a retrospective observational study, I'd like to compare the efficacy of drug A vs drug B, and was considering propensity score matching on age, gender, history of diabetes mellitus, and history of ...
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Analyzing data from a non-randomized sampling design (ecological monitoring)
I have 2 questions about analyzing data that was not randomly sampled from a population.
I work with "ecological monitoring" data that involves repeatedly taking measurements from the same ...
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How to identify natural experiments?
The motivation of this question is learn what to look for in deciding whether observational data can be used for causal inference (in the sense of Pearl).
Wikipedia describes a natural experiment:
A ...
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Does this study design lend itself to a logistic regression?
I have a cohort comprising of individuals who participate in a weight-loss program and their weight measurements are collected longitudinally for 12 months (not necessarily at the same time points). ...
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Can I use interrupted time series analysis on irregular reported medical data?
I am interested in using interrupted timeseries analysis on real world electronic healthcare records. My understanding of interrupted timeseries analysis is that data is time-ordered and gathered at ...
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Propensity score matching in a case-control study: can the number of matches per patient be correlated with a matching variable?
Say I am trying to investigate the association between antidepressants and achieving recovery in a depression programme. I have an observational cohort of depressed patients enrolled in the programme ...
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Power calculation for observational study vs using propensity score matching estimating treatment effect
For case-control study study, one can calculate sample size to determine power of the study with respect to particular estimator of interest. Suppose I am interested in treatment effect in case ...
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Basic understanding of control variables in observational studies
I'd like to understand the basic logic for control variables in observational studies.
According to Wikipedia, one should control for confounding variables, which "in this context means other ...
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Fixed-Effects Correlated with Another Dummy
Question regarding convention in econometrics.
Suppose I am running a two-way Fixed Effect (FE) model on a District-Year panel. Year varies from 2000 to 2010. Suppose I want to examine the effect of ...
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Comparing treatment effect using mixed effect model/gee/offset? Which one is better?
I think I have seen various posts indicating that comparison of treatment effect in observation studies should employ either longitudinal mixed effect model or GEE.
Suppose each individual is given ...
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Difference in Difference (DiD) estimator in cross country studies
How can we use Difference in Difference (DiD) estimator in cross country studies where we have to interpret results for each country separately?
Should this be one model using country dummy and ...
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Multi-centre survival analysis
I have question regarding survival analysis. I am looking at observational studies comparing patient survival who received treatments A or B at different centres (>10), for the same condition and ...
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Kaplan-Meier curves for retrospective studies
While doing a review i noticed that Kaplan-Meier curves are often used for retrospective studies in the medical field.
However, is it correct to do so even if the registry of data is not prospective? ...
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Is this a repeated cross-secitonal analyses?
I am using a dataset that has three waves divided by months (e.g., Wave 1 April to June 2021, Wave 2 July to September 2021, Wave 3 October to December 2021). Some of the participants have ...
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How to conduct my first data-analysis study?
I'm trying to improve my understanding of a few basic concepts in statistics (like statistical significance, the p-value, etc.) and to achieve that I decided to do a study myself (trying to learn ...
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How do I determine whether there is a significant difference between two sets of price data?
I am conducting a study where I am collecting prices from two groups of funeral homes in a particular state: in the first group, the homes I collected prices from are owned by families, and in the ...
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Multiple Sclerosis: study design to beta test a software
I am a beta-tester of a software that is intended to help the radiologist to interpret MRI reading of Multiple Sclerosis (MS).
MS is a disease that, over time, could lead to new lesions, expanding ...
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Is there a difference between ignorability and strong ignorability?
The whole idea around ignorability is still leaving me a bit confused. I did read this post from the site: Strong ignorability: confusion on the relationship between outcomes and treatment. It had ...
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