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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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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13 views
Permutation of treatment and control groups in R program [migrated]
I would like to do blocked randomization for 120 participants into 40 blocks of 3 participants each. 2 participants within each block is assigned to treatment (denoted by 1) and 1 participant is ...
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How does the TOST Equivalence Test Check Equivilence? [closed]
Under the TOST Equivalence Test, we check to see if the mean of differences between two measurements is (to a given significance level) close enough to zero:
$$H_0: |\mu_1 - \mu_2|> \delta$$
...
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0answers
24 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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8 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
25 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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1answer
15 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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0answers
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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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0answers
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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
37 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
63 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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8 views
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
29 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
76 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
49 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 ...
4
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1answer
62 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
32 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
20 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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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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0answers
51 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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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
28 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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0answers
45 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
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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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63 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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0answers
28 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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35 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
136 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
46 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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0answers
17 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
33 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 ...
2
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1answer
101 views
How to calculate treatment effect and its confidence interval for subgroups in a clinical trial using Cox regression models
Plenty of literature exists on how to interpret subgroup analyses in clinical trials. One example is in this thread. Unfortunately, I have not found any paper explaining how to perform a subgroup ...
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8 views
Medical or Intervention Study
A friend and I are trying to better understand proper design of a randomized trial, from beginning to end, with an eye to creating an informal one showing the benefits of a particular academic ...
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1answer
131 views
Warnings during propensity-score matching: 1: glm.fit: algorithm did not converge 2: glm.fit: fitted probabilities numerically 0 or 1 occurred [duplicate]
I am doing a propensity score matching(nearest neighbor matching) in R with simulated data and I keep getting the above warning messages. please I need help.
The following is my code
...
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21 views
Applying the Pocock boundary rule when p-value is not set to 0.05
I would like to set my new p-value threshold correcting for both multiple comparisons and interim analyses.
In a very easy example with two analyses (1 interim and 1 final) according to the Pocock ...
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1answer
20 views
Does an interim sample size re-estimation increase type 1 error if based on the overall event rate?
Suppose that a sample size is to be calculated for a trial: a presumed effect size summarizes the effect of intervention (relative risk RR $\exp(\theta_1)$), and background gives the rate of events in ...
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0answers
26 views
Sample size equation based on clinical paper
Hoping this one is easy, but I've been struggling to try to find what approach is being used online.
I'm trying to replicate the powering of a clinical trial for research purposes based on the below ...
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59 views
Poisson Gamma Distribution in R - Creating Enrollment Modeling Curve
I'm trying to create an enrollment curve for a clinical trial based on the following variables: Country start up timelines (staggered), Number of sites, Number of total subjects needed, Number of ...
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1answer
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Testing for the significance of treatment on intervention/target group compared to control group when group sizes are different?
So I have have been conducting an experiment of an interesting feed on livestock.
So essentially what I have done is, divided the total livestock $N$ in two different sized groups $n_1 $ and $ n_2$. I ...
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0answers
29 views
How does one perform a conditional power analysis?
Suppose a test statistic $Z$ will be compared to a standard normal distribution to evaluate whether a $p$-value achieves a statistically significant result at the $\alpha$-level. Based on an ...
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0answers
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Terminology when after inclusion to a RCT patient may undergo two different randomization procedures
I have trouble finding appropriate terminology for the following.
I want to investigate treatments A and B in disease X and treatments C and D in disease Y.
Diseases X and Y are basically two ...
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17 views
“Matching” groups in a clinical study
I have the following question regarding a clinical study in the Surgery department of an hospital:
1) I have two groups of patients: group A - comprising patients operated in 2016; group B - ...
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1answer
39 views
How can one summarize categorical variables with frequency variables in a clinical study?
Quote:
All eligible patients were analyzed. For the background of the patient population, categorical variables were summarized with the frequency and rate and continuous variables with fundamental ...
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0answers
37 views
Simulating survival meta-analysis data (with a random effect) [closed]
I would like to simulate survival meta-analysis in clinical trials on R but I'm not pretty sure of what would be the best way to do it and what would be fitting more the reality.
The data would ...
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0answers
7 views
phase 1 dose and schedule optimisation methods
Braun's 2007 Bayesian method describes simultaneously optimizing dose and schedule of a new cytotoxic agent (in a phase 1 clinical trial) https://journals.sagepub.com/doi/abs/10.1177/1740774507076934 ?...
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44 views
Calculating Sample Size for Cluster Randomized Trials with Person-level or Cluster-Level Outcomes
I have been looking for a formula to calculate the estimated sample size for a two-level cluster-randomized controlled trial with cluster-level outcome data. To my reading, several authors do not make ...
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0answers
31 views
Randomization in clinical trials
Randomization in clinical trials is a phenomena where each individual has equal chance to receive a treatment. How can you express randomization mathematically.
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1answer
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How to name a bias that is not quite the “immortality bias”
Strange question from me, but try to follow me.
I do not remember or name correctly a type of bias in cohort study which is pretty clear in my mind. I try to explain:
Let's assume that I want to test ...
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1answer
22 views
Propensity Score for observations in RCT study
In theory what would the $e_i$ (propensity scores) be, for $n_i$ observations already randomized into various treatment groups ?
I know $e_i$ (propensity scores) are calculated for $n_i$ ...
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4answers
226 views
Who is right, the statistician or the surgeon?
Consider the case described below, from Peacock (1972). This passage seems to imply the young statistician is making a smart, correct statement.
But is he?
