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.
427
questions
1
vote
1
answer
12
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 ...
- 313
1
vote
1
answer
31
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 ...
- 313
1
vote
1
answer
28
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, ...
- 94
0
votes
0
answers
28
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 ...
5
votes
3
answers
216
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 ...
- 313
10
votes
3
answers
80
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 ...
- 313
1
vote
0
answers
21
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 ...
- 1,173
1
vote
1
answer
54
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 ...
- 147
3
votes
1
answer
29
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 ...
- 8,470
1
vote
1
answer
45
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 ...
- 85
2
votes
2
answers
66
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 ...
- 281
-1
votes
2
answers
37
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.
- 94
2
votes
0
answers
41
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
84
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),
...
- 163
1
vote
1
answer
30
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-...
- 111
3
votes
2
answers
77
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 ...
- 33
4
votes
1
answer
159
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 ...
- 571
2
votes
1
answer
75
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 ...
- 23
1
vote
1
answer
39
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 ...
- 310
0
votes
1
answer
34
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 ...
- 4,405
6
votes
1
answer
57
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 (...
- 499
1
vote
1
answer
26
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 ...
- 13
2
votes
2
answers
91
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 ...
- 83
1
vote
1
answer
23
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 ...
- 571
1
vote
0
answers
23
views
Longitudinal data analysis with relationships information
I am part of a study where we are trying to understand the effect of social interaction on weight loss. The idea is to have two sets of Groups. In Group 1 there are group of people joining as a family ...
- 113
0
votes
1
answer
45
views
Intention-To-Treat and reporting of sample size
A question about semantics really I guess. Say a clinical trial is conducted according to ITT principles and a Full Analysis Set is defined as (for example) subjects that take at least one dose of ...
- 517
7
votes
1
answer
83
views
Explaining a Mixed Effect Model to a Non Statistician/Mathematician
I'm not a statistician, but I do have a basic understanding of biostatistics in the context of medicine and clinical trials. However, recently I came across a trial that is using a statistical method ...
- 71
3
votes
1
answer
53
views
Identical output for unadjusted and adjusted mixed effect model with lme4 in R
We have a rather mathematical/statistical problem and hope to get some help.
We have data from a multicenter randomized clinical trial where we compare single with combined treatments at 4 different ...
- 31
7
votes
2
answers
72
views
What is the statistical rationale for a phase 2 clinical trial?
There is a lot of contradictory information about the purpose of phase 2 clinical trials.
Many sources claim that the aim is to test whether a treatment works, and sample size calculators exist to ...
- 1,501
3
votes
2
answers
77
views
Is this explanation of a Non-Inferiority Margin Correct?
I'm relatively new to the field of biostats and was reading up on Non-Inferiority Trials and Margins and came across this explanation which is tripping me off a bit.
"For example, the oral ...
- 33
0
votes
1
answer
20
views
Sample size calculations for a pair-dependent discrete outcome
How do we calculate sample sizes (and power) for an outcome that is discrete and is only measurable between two individuals of a group?
Suppose we have $n_A$ individuals in group A, and $n_B$ ...
0
votes
1
answer
108
views
Subgroup analysis: post hoc test interpretation
I am modeling treatment effect in a hypothetical case where only a subset of the sample has disease-related impairment on the outcome of interest. I only expect treatment effects in this subset, but ...
- 145
0
votes
0
answers
24
views
Accounting for nuisance confounding variable in multi level model for crossed or multiple membership study
I am trying to use a multi level model for a study where participants take part in 3 separate sessions where they complete a cognitive task and I measure reaction time. During each session, they ...
- 1
2
votes
1
answer
92
views
linear regression vs anova or ancova in clinical trial
I analyze clinical research data,
This is a comparison of two treatment groups. The outcome is a continuous variable. We decided to adjust on predictors of outcome in imbalace, in posthoc (We assume ...
- 827
1
vote
0
answers
30
views
What is the sample size calculation for a discrete outcome (count variable)?
What is the sample size calculation for a discrete outcome (count variable)?
For example, I want to design a trial with a placebo and a treatment. The outcome is the number of days of treatment : 14 ...
- 139
3
votes
1
answer
82
views
Test for synergy using Bliss independance model for two drugs
I have a dataset of 40 patients which receive 4 different treatments, group 1, is placebo, group 2, drug A, group 3, drug B and group 4, drug A+B. Only one dose from each drug and combination. I would ...
- 113
0
votes
1
answer
89
views
Analyses of continuous variable like time to event within clinical setting
My apologies if this has been previously answered.
I am fairly new to statistics of clinical trials and I want to know how the expert statisticians handle continuous variables like "time to event&...
- 4,405
1
vote
0
answers
15
views
Score Questionare for different age groups combined [closed]
Lets say we have two questionares for two different age groups. One has 100 items the other 150 items, where we can answer each question with 0 - 2. Then we calculate the mean value of all answers ...
- 11
0
votes
0
answers
38
views
How to extract pre/post correlations at each level of a multilevel model? (Cluster RCT - two levels - children clustered within schools)
I am analysing a randomised controlled trial using a two level linear mixed model. This is a two arm, pre-post design, where the post test is the primary outcome and we control for pre-test as a ...
- 333
1
vote
0
answers
27
views
Why the mixed effect model and the meta-analysis model generate different results given the dependent variable is uncorrelated?
I have a data that looks like the following:
...
- 669
4
votes
1
answer
105
views
How are group sequential analysis, random walks, and Brownian motion related?
Assume that I am planning a clinical trial comparing two groups using a binary outcome. I will do the $\chi^2$ test after 3 equal enrollment intervals: interim test #1 after $m_1$ enrollments in ...
- 326
0
votes
1
answer
184
views
How we do the Mixed ANOVA post comparison
I am learning and doing the Mixed ANOVA using Python pingouin under a clinical example dataset that contains one between factor (drug: A, B, C) and one within factor (Time: T0, T1, T2, T3, T4) from 5 ...
- 1
2
votes
0
answers
115
views
Time-fixed effects in a randomized controlled trial?
When analyzing the results of an RCT, it is not uncommon to see a unit (e.g. cluster) fixed effects in the linear regression model but I have never seen time fixed effects while time FEs are pretty ...
- 45
3
votes
1
answer
62
views
Post hoc adjustment in clinical trial
I would like to make an adjustment on a baseline variable (which has a small imbalance).This is a post hoc adjustment (I recognize, however, the limits of this adjustment which has not been pre-...
- 827
1
vote
0
answers
16
views
Clinical drug trial data analyses
I am new to clinical drug trial data analyses.
The goal is to learn the analyses of clinical drug trial data, that incorporates demographic data, efficacy data and co-morbidity data at the least.
I am ...
- 4,405
1
vote
0
answers
26
views
Clinical trial power: Equivalence test with noninferiority for adverse events
I need to power noninferiority as it relates to adverse events in a trial for two independent (failure) proportions. Here are example inputs:
Treatment $P_1$=0.05, placebo $P_2$=0.20, adverse events $...
- 136
3
votes
1
answer
117
views
Why does unmeasured mediator–outcome confounding possibly remain even in randomized control trial
I have heard the following but I cannot be totally convinced. The DAG is shown below.
$Q:$ Why does unmeasured mediator–outcome confounding possibly remain even in randomized control trial? Should ...
- 1,365
2
votes
0
answers
52
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 ...
- 1,365
1
vote
1
answer
33
views
The impaction difference between image of random variable and clinical practice in clinical trial
In the clinical trial design, we often make assumptions about clinical endpoints. For example, we may assume the blood pressure followed a normal distribution, such as $ X \sim N(\theta, \sigma^2)$, $...
- 71
0
votes
0
answers
22
views
Can I calculate precision from prevalence and misclassification rate?
If I know $P(D+)=P(disease+)=0.001$, a test is accurate (meaning the test agrees with the truth) 99% of the times, could I calculate the precision $P(D+|T+)=P(disease+|test+)$?
$P(D+|T+)=\frac{P(T+|D+)...
- 135