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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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
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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0answers
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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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
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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0answers
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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1answer
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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0answers
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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0answers
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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2answers
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 ...
1
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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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0answers
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 ...
2
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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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0answers
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 ...
2
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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
12 views
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
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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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
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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0answers
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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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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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
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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2answers
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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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 ...
0
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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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0answers
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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2answers
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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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22 views
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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2answers
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 ...
4
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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 ...
3
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0answers
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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1answer
67 views
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 ...
