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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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34 views

Minimization randomisation in trial, what to do if dropout or missing data?

I have been asked a question on minimization randomisation in a randomised control trial. If the randomisation has allocated thirty participants to sham or treatment, but then subsequently it is ...
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1answer
17 views

Power calculation & study design for study with rare safety outcome

An RCT is planned to compare a new/repurposed drug to placebo on the basis of mechanistic findings. Limited safety data exist. The primary efficacy outcome requires the recruitment of ~200 ...
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1answer
26 views

How to specify a risk model?

I'm reading this article. The authors indicated that for a random sample of 12 characteristics and 3600 patients affected in two arms (control and treatment arm), they fitted a risk model consisting ...
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1answer
22 views

How can one define the power of a randomized clinical trial?

The statistical power of a study is a measure of the ability of a randomized clinical trial (RCT) to detect a difference statistically significant of the treatment effect in the treatment arms. How ...
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22 views

Poisson regression for # of acute toxicities as outcome variable?

I have a data set of N=200 comprised of patients who either received Treatment A (N=50) or Treatment B (N=150). I have treatment toxicity outcomes (binary yes or no) across 4 domains: hematologic, ...
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O'Brien Fleming Interim Analysis Interpretation with PROC SEQDESIGN

Quick question about the output of PROC SEQDESIGN. I was playing around with the O'Brien Fleming method trying to understand how we can interpret the results spit out by SAS for a mock study with ...
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14 views

Logistic regression for factorial design: interaction and main effects of treatments

I have a factorial experimental design with 4 groups: (1) Controls, (2) Treatment A, (3) Treatment B, and (4) Both treatments A and B. A total of 100 patients were randomly allocated in a balanced ...
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13 views

how to calculate critical value for HR given number of events?

Can anyone explain to me how this formula is derived? The critical value of HR (1:1 randomization) from number of events: exp(-2*abs(qnorm(0.025))/sqrt(d)), where d is the number of events
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24 views

(Minimum) Sample size in a clinical study, rule-of-thumb

I was asked this question and I am not sure about my answer that is why I am asking it here. An institute wants to conduct a clinical study. This study has most likely three treatment arms. The design ...
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1answer
30 views

What sample size is needed for randomization to be meaningful?

This study randomised 17 participants to 3 treatment arms. What sample size is needed for randomization to be meaningful? As an extreme example, randomly assigning 4 individuals to 2 treatment groups ...
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2answers
46 views

Joint models with time to progression

Consider a RCT (Randomized Controlled Trial) which aims at assessing the efficacy of a drug in patients suffering from a given cancer. In this trial, $p$ individuals are observed at several time ...
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30 views

Analysis of pre and post treatment

I have the following data: A random group of patients with a certain disease who receive a drug at a certain time. Dose of the drug given to the patient. This drug has an affect to the heart which ...
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16 views

Looking for statistics suggestion for data set: EEG “Diagnostic” measurement comparison - non-parametric/ordinal - large proportion of zeroes

I was hoping to get some input on handling a particular data set that falls outside of the purvue of the a lab I am apart of (usually outcomes research). The data consists of a pair of repeated ...
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19 views

An investigator planned repeated measures on n individuals with K time points but the sample size changes due to death-event after each time points?

Suppose an investigator planned repeated measures on n individuals with K time points but the sample size changes due to death-event after each time point. The investigator seeks to predict the cause ...
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22 views

randomization of clinical trial with two conditions and two visits

I would like to discuss the problem of randomization of a clinical trial. Let's say we start with 130 healthy subjects. Each subjects will be examined twice, a few years apart (which means there are ...
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25 views

State the overall alpha after interium analyses

Suppose a trial investigator wants to analyse the primary outcome (morning peak flow at 6 months) after the trial has been running for 1 year, 18 months and 2 years using alpha=0.05 each time, and ...
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1answer
38 views

Linear mixed model in clinical trials - only one is feasible?

Repeated measurements of some continuous variable of interested is very common in clinical trials. Usually patients are randomized between treatment arms. Hence it is reasonable to assume that all ...
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38 views

Controlling the allocation bias in small RCT

In order to contain the allocation bias, I would like to understand if it is possible to have a randomization process during the patients enrollement controlling ...
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1answer
42 views

Clinical trials simple randomization scheme simulation [closed]

I'm trying to do 1000 simulations for how to randomize 100 patients to two treatment groups (A and B) using simple randomization scheme (with probability 0.5) and figure out what is the chance of a ...
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38 views

How to use Binomial Distribution in clinical trials

I would like to ask your opinion about the use of a simple likelihood binomial estimation in a medical paper. DATA: Let assume to have 150 patients, each patient has been treated, thus we get an ...
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1answer
57 views

Correlation between logrank (log-rank) test statistics with common control

Say I have a $K$ arm experiment that generates survival (time-to-event) endpoints. There are $K-1$ experimental arms and a single control arm. Say I compute a log rank test statistic comparing the ...
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20 views

Interim analysis and alpha spending in group sequence design of clinical trials

In group sequential design, does the type of interim analysis affect the alpha spending for each look? I tested in ADDPLAN, with two interim analyses, specifying "stopping for futility" or not does ...
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1answer
33 views

Not including main effect term in subgroup analysis?

I know there are plenty of previous Cross Validated posts regarding if one must include the main effect term if the interaction term is included. The general consensus is: no if you have a very good ...
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12 views

What is the relationship between risk ratio and weight of evidence?

I've been reading about risk ratios as typical measures in clinical settings. In finance and credit literature, there is the weight of evidence measure to encode and study variables. Is there a ...
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1answer
312 views

advantages and disadvantages of IPTW vs propensity score matching?

what are the advantages and disadvantages of IPTW (Inverse Probability of Treatment Weighting) comparing to PSM (propensity score matching) in dealing with confounding variables?
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23 views

how to synthesize a virtual control arm from multiple historical trials with different treatment in their control arms

We want to synthesize a virtual control arm for a single arm study, and we found two trials with data available that targeting the same population. One trial used Placebo+Standard of care in the ...
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16 views

how to do re-randomization test for trials used adaptive minimization with unequal allocation?

Re-randomization test is often chosen to validate the results from a study was randomized by adaptive minimization. In the case of of unequal allocation (like 2:1), it is more complicated because the ...
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Time-to-event statistical test for toxicity within a 12-month time frame?

I am performing a retrospective study and this is my hypothesis: among patients with metastatic melanoma, antibiotic exposure within the 3 months prior to immunotherapy increases the risk of therapy-...
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1answer
43 views

Statistical Significance in Table Ones

I have a question about statistical and clinical significance. In a non-clinical trials setting (e.g. observational), if the sample size is large for both groups (assume 2 groups for simplicity) ...
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3answers
81 views

Study design question: What's the best design to assess harm of an exposure?

Was hoping to get your thoughts on a prospective study design. Here's some basic info: Population: Patients with melanoma receiving immunotherapy. Exposure: Steroids within 3 months prior to first ...
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How do I use clinical trials as random effects in a cox regression model stratified according to trial for an individual patient data meta-analysis? [closed]

I am performing an individual patient data meta-analysis and pooling several trials. I have the data all combined in a single data set and want to fit it in a Cox regression model stratified according ...
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1answer
32 views

Effect size for a trial with pre and post measurements

I have recently been told two different ways to prepare data for calculating effect size (Hedge's g) of a placebo-controlled trial: use post-intervention means of the assessment values for both ...
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1answer
87 views

In what sense does interim monitoring of clinical trials “cost” a Bayesian?

I have read (and will seek a specific reference on the subject) that unlike Frequentist trials, Bayesians can continually monitor data as it accrues. A Frequentist tries to control, and thus ...
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2answers
51 views

Significant interaction, inconsistent with plots/raw data

I'm analyzing experimental data and the model shows a significant treatment effect, but the raw data and graph of the effect don't seem to match it. I want to understand why. I've been looking at this ...
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1answer
70 views

Randomization in an RCT: How harmful is it to try different RNG seeds?

Background I was asked to perform the randomization for a small study with 3 conditions $A$, $B$ and $C$. The three conditions are three different smartphone types. The participants enter the study ...
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1answer
33 views

Powering versus statistical significance in clinical trial design

I think I have a simple question that I have not seen directly answered elsewhere, and as a stats beginner, I'm wary to translate answers that are not directly answering this question - apologies if ...
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1answer
23 views

ANOVA 3X3, what are the steps (by hand)

For my dissertation project, I have proposed a randomised controlled trial. My independent variable consists of 3 groups: one receiving AVATAR-cognitive therapy, one receiving Cognitive Therapy, and ...
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29 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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52 views

Specificity and sensitivity in a retrospective clinical diagnosis study: How many samples do I need?

I would like to analyse the survival at 2 years after undergoing 1 of 3 diagnostic methods for diagnosing two related conditions: condition IBD (can respond to drug A) or condition SLC (can respond to ...
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8 views

I want to design a randomised controlled trial proposal . So one group receives a new intervention(Cognitive therapy+AVATAR)

So one group receives a new intervention(Cognitive therapy+AVATAR). My first thought was to use another active control group who receives Cognitive therapy and one Treatment as Usual group. Should I ...
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1answer
44 views

Linear mixed effects model for trial [R]

I have finished a trial where we measured continously measurements like blood pressure ...
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3answers
143 views

Assess temporary effect of treatment

Imagine that I have a treatment that reduces the likelihood of response to a stimulus. This could be anything you like, but the simplest example is of a treatment (e.g., hand washing, mask wearing, ...
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1answer
83 views

Multi-arm extension to Simon's single-arm two-stage design?

For adaptive phase II clinical trials with binary endpoint, the Simon's two stage design is well-known (Simon 1989) and easy to implement. However, I was wondering, whether there are multi-arm two-...
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94 views

Calculate odds ratios and P-value for interaction across multiple separate subgroups

I'm trying to understand/replicate an adjusted logistic regression analysis where a treatment effect is estimated separately in a number (>2) of subgroups and estimating an overall P-value for ...
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31 views

How do I divide a density/frequency plot?

I have a frequency plot, which is essentially a smooth histogram. There are three very clear features (divided with a line by eye). Please note, there are two groups, male and female. The data used to ...
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46 views

A multi-armed bandit problem in clinical trial

Suppose that we have two drugs A and B with levels $i=1,\ldots,I$ and $j = 1, \ldots, J$, respectively. These two different drugs are given to patients in a clinical trial. $p_{ij}$ is the prior dose ...
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2answers
170 views

Cox proportional hazard analysis with non-uniform samples; power analysis

We have a study involving 10,000 patients, 5,000 of them treated with drug A and 5,000 with drug B. We want to know if drug A is more effective than B. The median time to event (death) after treatment ...
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1answer
99 views

sample size calculation in 3-arm survival analysis

In a 3-arms clinical trial, with time to event data, either A is superior to C or B is superior to C it will be considered significant. No need to compare A and B. I know how to calculate the sample ...
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18 views

Chi Square embedded in an ANOVA model?

I have treatment->outcomes count data, which is obviously modeled by a chi squared, but there are several separate ones, let's say 3. I could run 3 separate chi squares, but I want to ask what would ...
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1answer
36 views

MCMC sampling with a probability density function that have potential negative values

My question might be quite strange, but I will expose you the complete issue in order for you to help me. I am in the context of a parallel randomized clinical trial which aim is to compare two ...