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Questions tagged [clinical-trials]

Clinical trials are studies designed to test the safety and efficacy of new clinical interventions such as drugs or medical devices.

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Defining clinical follow-up: Fixed Period vs. Maximum Duration

We are retrospectively analyzing data of around 1100 patients operated between 2017 and 2023. We analyzed follow-up documentation until 2024. This means that patients operated at a later date will ...
Philipp's user avatar
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0 answers
17 views

How to estimate the CI of RERI [closed]

This thread is involved in statistical tech to measure interactions. The RERI is short for "relative excess risk due to interaction". I know it's quite a bit difficult to understand but, to ...
Tom Hsiung's user avatar
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1 answer
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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
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How to combine intention-to-treatment randomization with block randomized experimental designs for within-differences in Power Analysis

I want to calculate the power for my experiment. Within multiple blocks of similarities (e.g., same gender, same pre-treatment outcome), respondents get the opportunity to take part in a treatment. As ...
canIchangethis's user avatar
1 vote
1 answer
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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
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1 vote
1 answer
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Moderator Analysis in Cox Regression

Imagine an RCT with two groups with a time-to-event endpoint. The (pre-specified) strategy for analysing this trial is a Cox Regression using common covariate adjustment to reduce outcome ...
Survival's user avatar
  • 149
1 vote
1 answer
28 views

How the randomisation probability is updated for each new patient entering adaptive clinical trial?

Disclaimer: You may need to read the entire paper to answer this question :) I am reading this paper to learn about adaptive clinical trials. Here in page 1723 under "Statistical methods" ...
Chirag Patil's user avatar
1 vote
0 answers
25 views

What are the fundamental differences of Kaplan-Meier testing versus tests of proportions?

Suppose my study will recruit 50 patients and monitor them for some outcome that may crop up at any point in time. My null hypothesis is that the proportion of event-free subjects at time $t=12$ is ...
AdamO's user avatar
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In a 2 arm pre-post RCT, is an interaction test on an ANOVA the same as a t-test of the change scores?

Say you have a 2-armed pre-test post-test control trial design. You want to test the effect of group allocation on the outcome variable. I simulated a version of this in R, using 3 different methods: ...
Joel Phillips's user avatar
2 votes
2 answers
36 views

Evaluate blinding using Fisher's exact test

In a clinical trial, there are 3 groups A, B & C, but only 2 interventions which participants are blinded to. Everyone in group A got active treatment, and everyone in group B & C got placebo. ...
RainDeer's user avatar
1 vote
0 answers
49 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
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Second Generation P-values in the Context of Statistical Evidence and Sample Size

I am currently doing research on statistical analysis, and I have come across the concepts of Second Generation P-values (SGPVs) introduced by Blume et al. I understand that these are used to ...
Maale Faustus's user avatar
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47 views

When to use paired samples tests? Specific case in clinical research

I am working on the analysis of an observational clinical study. It is basically a control/intervention study, where the intervention group received a novel protocol. In order to assess its ...
LevG's user avatar
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5 votes
2 answers
218 views

Double Blind Studies & Confounders

I'm currently reading The Book of Why, and on pg 147-149 it talks about double blind RCT being very highly regarded in experiments, especially in the way it address confounders. In theory, I can ...
ron burgundy's user avatar
1 vote
1 answer
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Is Assessment Bias a type of Observer Bias?

Based on the definitions of assessment bias and observer bias I have found bellow, seems like assessment bias is a type of observer bias? Assessment bias: If the observer knows the treatment being ...
a12345's user avatar
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Can you derive the standard error of odds ratio, from a method (Kraemer and Kupfer) that derives Risk Difference (and its SE) from continuous data?

Let's say that we have a RCT trial going on and the outcome is a continuous variable. In this paper https://pubmed.ncbi.nlm.nih.gov/23045205/ there are 4 methods that calculate approximated odds ...
SpartacusKD's user avatar
1 vote
1 answer
39 views

For a clinical study, What statistical analysis methods should I add or change [closed]

"I am conducting a statistical analysis of a clinical study where the dependent variable is binary (whether a myocardial infarction occurred). As a novice, I initially learned specific ...
zhiheng yi's user avatar
4 votes
1 answer
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Why sample size calculation for RCT almost always uses simple univariate test?

I noticed that most RCTs use simple univariate statistical test to perform sample size calculation. For example for continous outcome, z-test may be used. But eventually for final analysis, mixed ...
tatami's user avatar
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2 answers
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Null hypothesis in clinical trial question

Consider a clinical trial where we want to study the evolution of the occurence of some event during two time periods, with and without treatment. We know that, not only a difference close to 0 won't ...
geaidc's user avatar
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5 votes
1 answer
293 views

How to interpret a nonsignificant interaction effect with significant main effects?

I have the results of a 2*5 mixed ANOVA drug trial, where there’s a non significant interaction but main effects of both time and group. Scores were taken before and after trial (time). 4 drugs were ...
Harry's user avatar
  • 51
3 votes
1 answer
123 views

superiority margin in sample size calculation

I've to calculate the sample size for a superiority trial. I've found many online calculator, but each one gives a different result and I don't understand why. For istance, this one: https://riskcalc....
ArTu's user avatar
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1 vote
1 answer
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Example of sample size calculation for a randomized, placebo-controlled trial

I am trying to reproduce the calculations for sample size in the following article : n = sample size required in each group p1 = proportion of deaths in group Azithromycin p2 = proportion of deaths ...
Happy Cretine's user avatar
0 votes
1 answer
35 views

Help on diivergence in the Paired T Test sample size formula between Machin and others

for a pre-post study, continous endpoint (assume normality). I would like to detect a difference of 50 (mg/dL) and SD of the changes could be easily 20 mg/dL (for ex.). the issue is, according to ...
Alex Ortega's user avatar
1 vote
1 answer
53 views

What to do when my sample size is small to demonstrate an equivalence study

I'm analyzing data from a study comparing 5 treatment arms. Women receiving ovarian stimulation for in vitro fertilization at different phases of the ovarian cycle. The treatment efficacy endpoint was ...
Seydou GORO's user avatar
0 votes
0 answers
37 views

Log-rank vs Cox hazard model for survival analysis [duplicate]

I'm a medical oncologist and had some doubts concerning the stats behind clinical trials design. My question concerned the use of log-rank vs. univariable Cox-regression to compare the survival curves ...
DK80's user avatar
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3 votes
0 answers
36 views

Techniques for Stopping a Diagnostic Study for Safety

I'm working with a group of physicians who are interested in evaluating a new diagnostic tool for detecting colon cancer in older patients. The gold standard to detect colon cancer is with a ...
Demetri Pananos's user avatar
3 votes
1 answer
29 views

How can I tell if a clutser-randomised crossover trial has made a unit of analysis error?

I am studying the following paper: https://jamanetwork.com/journals/jama/fullarticle/2698491 This is a cluster randomised control trial with crossover. I want to ensure they have not made a unit of ...
user356816's user avatar
1 vote
1 answer
40 views

What would be the effect of assuming the wrong homoskedastic/ heteroskedastic spread of data?

If a cluster trial had homoskedastic data, but the regression model used by the authors used 'robust standard errors' intended for use with heteroskedastic data (or vice-versa), would the implications ...
user356816's user avatar
2 votes
1 answer
144 views

How to handle the residual covariance structure in a mixed model with repeated measurements?

In clinical trials and other areas of applied statistics, we often need to model longitudinal data. In most introductions to modelling longitudinal data with mixed effects models that I have seen, ...
underflow's user avatar
  • 313
0 votes
0 answers
41 views

R model for proportional odds methodology for scale variable that allows for variable improvements

I'm looking to understand what would be the most appropriate R model for fitting a clinical dataset in which the dependent variable is the change in a 5-point scale and the end of treatment. The data ...
wingsoficarus116's user avatar
6 votes
3 answers
234 views

Are post-hoc adjusted analyses more valid than initial analyses?

Many papers design a methodology to detect a difference between $2$ groups regarding a primary outcome. This result is then given a $p$ value to denote statistical significance. Some papers then go on ...
user356816's user avatar
10 votes
3 answers
107 views

Can you legitimately claim to have used intention-to-treat analysis in a cluster randomised trial if recruitment occurs after randomisation?

In cluster-randomised clinical trials it is often the case that 'units', be they hospitals, practitioners or primary care centres etc., are randomised to the intervention or control arms prior to ...
user356816's user avatar
1 vote
0 answers
31 views

balanced and unbalanced dose response experiments

Consider a dose response study where there are four active treatments (from the highest dose and lowest dose) and also a control. One goal is to test the hypothesis that treatments are more effective ...
user13154's user avatar
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2 votes
1 answer
119 views

Comparison of Kaplan-Meier and Cox models for survival analysis

I am looking at the results for survival analysis for leukaemia patients, categorised based on Copy Number Variation (CNV) levels using array comparative genomic hybridisation. So far I have plotted ...
camhsdoc's user avatar
  • 409
3 votes
1 answer
101 views

Sample size estimate for difference of hazard ratios

I'm planning a Kaplan-Meier analysis and need to determine an appropriate sample size for the study. I have two treatment arms and want to show that there is a differential biomarker effect depending ...
Nuclear Hoagie's user avatar
2 votes
1 answer
54 views

In a 2-arm clinical trial where ten centers recruited patients, how does one test that two distributions are statistically similar?

There are two arms in a clinical trial. If ten centers recruited subjects. How do I test in R that distribution across centers into two arms are statistically same? The distribution appears ...
abcihep's user avatar
  • 95
2 votes
2 answers
182 views

Statistically testing for differential attrition in R?

Context I have a randomized controlled trial with three groups and three time measurements (pre, post, follow-up). I noticed that from pre to post, and then from post to follow-up, the attrition rates ...
rempsyc's user avatar
  • 281
-1 votes
2 answers
78 views

What are the current major issues and controversies in clinical trials design and analysis? [closed]

As per the title, I would like to know what are currently the major issues and controversies in clinical trials design and analysis.
underflow's user avatar
  • 313
2 votes
0 answers
63 views

Book recommendations for the design and analysis of clinical trials for drug development

I am looking for some recommendations for books about the statistical analysis of clinical trials data, that also covers the design of clinical trial studies. I am familiar with Stephen Senn's book, &...
2 votes
1 answer
281 views

Sample size for 2-arm 2-stage trial: R package Trialsize vs rpact vs gsDesign

Which sample size calculation is correct? Intended design: Superiority two-arm trial between drug A (intervention) vs drug B (comparator), outcome is binomial (response or no response to treatment), ...
saifulsafuan's user avatar
1 vote
1 answer
48 views

Doubt on checking linearity assumption in a mixed-ANCOVA design

I am a PhD student and I have to run a mixed-ANCOVA on some questionnaire scores (my dependent variable) according to the following model. Factors of ANCOVA are (a) Timepoint (pre-intervention, post-...
Fil's user avatar
  • 121
3 votes
2 answers
202 views

Linear Mixed Models for randomized clinical trial

I am working on analyzing data from a randomized clinical trial which is studying the effect of a mesh type on patient-reported pain. The 2 study arms are the 2 different meshes (biologic and ...
S. Patel's user avatar
4 votes
1 answer
162 views

In clinical trials, what is the benefit of using a composite rather than individual outcome

I have read that composite outcomes are common in cardiovascular trials because they give a holistic view of a treatment effect. Assuming outcomes are frequent enough for statistical power to not be ...
Geoff's user avatar
  • 741
2 votes
1 answer
102 views

Sample size and minimal clinically important difference

my study is a randomized controlled clinical trial involving 3 groups in parallel. Sample size was calculated based on blood cholesterol endpoint as 20 participants per group. However my problem is to ...
user14845003's user avatar
2 votes
1 answer
133 views

Sample size calculation for a three independent arm RCT with a categorical outcome

I have three study arms on interventions A, B, and C, which are independent of each other. The primary outcome is categorical (positive or negative). The null hypothesis is A = B = C. From prior ...
Bradex's user avatar
  • 340
1 vote
1 answer
57 views

Logistic Regression to identify significant covariates(variables)

I am working on logistic regression to identify the most cucial genes that can predict the response of stimuli. I have a workflow that looks fine to me but I want inputs from the people who have more ...
Angelo's user avatar
  • 4,525
6 votes
1 answer
68 views

Ran out of envelopes in randomized control trial

We are conducting a randomized control trial (RCT) comparing treatment vs. control from 4 sites (A-D). We have planned for 100 patients from each site. 100 envelopes of treatment assignment (...
user167591's user avatar
1 vote
1 answer
46 views

Using multiple imputation on components of a derived variable

I have a time-to-event variable, where the occurrence of event is determined by 5 numerical components measured at pre-specified timepoints. Missing values are observed for some components at some ...
Will_Zhang's user avatar
2 votes
2 answers
186 views

Why do we use term "arm" to express different treatment "group" in clinical trials?

I'm reading papers about randomization in clinical trials. I'm curious why we use the term "arm" such as in "two-arm trials" to express "treatment and control groups". I ...
Voyager's user avatar
  • 305
1 vote
1 answer
31 views

What is the formula for the expected variance from a randomised clinical trial with a single continuous covariate

I'm reading Stephen Senn's book, Statistical Issues in Drug Development, and come across this formula for the expected variance of a randomised clinical trial, with a fitted single continuous ...
Geoff's user avatar
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