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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38 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
58 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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21 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
19 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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11 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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49 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
27 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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44 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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60 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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59 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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25 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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32 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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126 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
27 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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15 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
31 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 ...
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1answer
80 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
118 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
18 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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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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52 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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27 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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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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35 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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35 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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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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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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40 views

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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20 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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143 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?
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18 views

Exploratory Factor Analysis for Smoking cessation RCT?

So I'm planning a RCT where I'm evaluating a smoking cessation application intervention vs usual care among adolescent smokers. For my statistical analysis I'm looking at the point prevalence of ...
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1answer
83 views

Average treatment effect using relative risk difference?

So I'm designing a RCT to evaluate the effectiveness of a smoking cessation intervention. For my analysis I've decided to look at three different things. 1) the point prevalence of smoking cessation ...
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1answer
99 views

Calculating trial size with the pwr package (R)

I'm attempting to calculate n for a trial in medical imaging comparing two different imaging modalities. I've never done this before, so I'm not sure how to approach this and interpret the result. ...
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9 views

Choice of model for prognostic value of asymptomatic recurrence detection

I am involved in the final step of a project that evaluates the prognostic value of asymptomatic vs. symptomatic recurrence detection; all subjects experienced recurrence. The project proposed a ...
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14 views

Does Intention-to-treat apply to the cases that should have been excluded but not able to do so during recruitment?

I am working on a pharmacist-supported new medicine randomised trial. One of the criteria during the recruitment was that if a patient used medicine previously, he/she should not be recruited. ...
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How to understand a before-after effect in a longitudinal medical dataset

I am after some suggestions on what statistical analysis I can perform to show a before-and-after effect in a longitudinal electronic healthcare record (EHR). I have N number of EHRs, of varying sizes/...
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What role(s) does Statistical Computing / Computational Statistics play in Clinical Trials?

I am going to pursue a PhD in Statistics, and the two fields that I am really interested are Statistical Computing / Computational Statistics and Clinical Trials (mainly because I like doing ...
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1answer
54 views

Per protocol or Imputation when missing is small (<5%)

if ~2% of my data is missing on the outcome (continuous scale), out of a total of 200, two in control and three in intervention group, do I need to impute? Or can I make a case that with such small ...
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1answer
20 views

gender specific treatment arms in clinical trial

if we were designing a clinical trial to compare an old and new treatment and there was strong a priori evidence of a treatment gender interaction (ie new treatment does better than old in men, worse ...
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86 views

Why are p-values in clinical trials often based off of LSmeans

Very often I see clinical trials quoting p-values based upon the differences in treatment effects using the LSmeans. To improve my understanding of this I attempted to learn how to calculate LSmeans ...
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1answer
608 views

Chi Square versus Poisson distribution

In a study which analyses the effect of Lithium on suicide rates, the results were the following: Placebo group: 3 suicides in 83 patients Lithium group: 0 suicides in 84 patients My first approach ...
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79 views

How does the “Carlisle method” work? (used to detect improper randomization in studies)

The NPR news article Errors Trigger Retraction Of Study On Mediterranean Diet's Heart Benefits refers to something it calls the "Carlisle method" of analyzing results of published studies to look for ...
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The Mediterranean diet - statistics issues with the updated paper

In 2013, a group of researchers published a paper with results on a randomized trial of the Mediterranean diet, finding that it appears to have significant health benefits. Today, they retracted ...
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Systematic allocation of treatment: is there a chance of biasing a design?

When we speak of the benefits of randomization, we talk about the balance of covariates so as to mitigate the possible confounding due to selection of treatment. That is, if a design were replicated ...