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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No previous information in a clinical trial

I'm conducting a clinical trial with a treatment group and a placebo group and calculated the sample size based on a previous study. However, I would like to add two more new placebo groups with ...
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Calculate sample size for clinical trial without raw data

Usually, we calculate the sample size needed for a clinical trial based on a former clinical trial which shows there is a significant effect. What if there is no such a trial? What if there is no ...
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How does a patients distribution affect a trials distribution?

For example, the trial has a normal distribution with mean 10 and stdev 35. However, that distribution is calculated using the average of each patients measurements. Say each patient in the trial has ...
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Synthesis without meta-analysis, z-score for 2 proportions?

I am doing a meta-analysis. One of the outcomes I meta-analyzed involved pooling multiple types of related complications. There wasn't enough data to pool the individual reasons for the complications, ...
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Testing and conidence interval in a clinical trial

In a clinical trial, let's say I want to test $$H_0: \mu_1 \leq \mu_2$$ $$H_1: \mu_1 > \mu_2$$ $\mu_1$ belongs to the placebo group and $\mu_2$ belongs to the trt group. I used an independent two-...
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LME Quantifying differences between and within intervention groups

I am new to mixed-effects models and trying to ensure I understand them appropriately. I am analysing the results of a 2x2 cross-over intervention study. Essentially, I have 50 subjects who completed ...
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Treatment: Mean AND variance should be optimized. What test to use/how to use (for instance t-test)?

Assume a research on the effect of applying a treatment to improve health by normalizing level of some vitamins in the bodies of some people. We measure initially the level of the vitamin of sick ...
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Survival analysis mostly censored data

I have (another) question regarding survival analysis: If I had two groups of participants (rather small, less than 100, well-matched apart for one or two covariates) exposed to treatments A and B ...
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When the anticipated sample size is not reached in a clinical trial

How to justify precisely a situation where the expected sample size is not reached? For example, the sample size for our study protocol was determined on the basis of a fixed statistical power of 80%. ...
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In a randomized trial, should we exclude random intercepts and use only slopes?

Let's say I have a longitudinal study, with patients assessed at several time points, which goal is to compare the treatment vs. placebo. If, theoretically, I used a mixed model to analyse the ...
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Question about P value

If it is said that a trial prespecified one-sided overall type one error of 2.5%, and the trial was designed to assess superiority, so one sided tests were specified for the alternative hypothesis, ...
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Can parallel designs be considered the "gold-standard" for RCTs

Statistically speaking, are parallel designs the "gold-standard" for RCTs? I mean statistically in opposition to financial, ethical or operational aspects. The only drawback I see for (...
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Disease Control Rate for a Clinical Trial problem

Recently, I have come across a 2-armed clinical trial problem which attempts to find a "Disease Control Rate" (DCR) for patients in the treatement and placebo arms. On the Internet I found ...
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Two arm Clinical Trial hypothesis [duplicate]

I am having a clinical trial that is devised in such a way that the treatment is considered effective by physicians, if its "restricted mean survival time" is atleast 5 units more than ...
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RCT using simple Randomisation, can extra participants be added?

I have been asked to perform the randomisation for a small RCT using simple randomisation. There are 100 individuals to randomise to one of two arms (control vs intervention). The researchers have not ...
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Clinical trial study hypothesis

I am having a two armed clinical trial where I would like to measure the difference between restricted mean survival times for placebo and treatment arms. If the difference is atleast "5" ...
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Inference for the average treatment effect for Bernoulli trial

In the book of Imbens and Rubin, they discuss four common classes of assignment mechanisms that fit into this framework: Bernoulli trials, completely randomized experiments, stratified randomized ...
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Median Survival Time for Clinical Trials

I have a Clinical Trial where I'll be comparing a drug vs placebo. Then I intend to run a Log-rank test on it. Now for the sample size calculations, I would be requiring the hazard ratio and the ...
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Statistical methodology for a 3 arms clinical trial

I am struggling to finalise a statistical framework/methodology that would be best suited to analyse a 3 arm clinical trail data. The problem is as follows, I have two clinical trails, parallel ...
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How to find shape and scale parameters for a Weibull distribution in survival analysis

I am to run a superiority clinical trial and I want to fit a parametric model under the Weibull Distribution. But I am confused about how should I find the shape and scale parameters for the Weibull ...
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Are the arguments that placebo can be unethical mistaken?

There seem to be two ideas of placebo - or the treatment received by a placebo group: A "simulation" of a treatment using saline or sugar pill so that subjects in a clinical trial can be ...
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How is the O'Brien-Fleming constant calculated and how does the procedure control error rates?

O'Brien-Fleming is a commonly used interim analysis procedure in clinical trials. The procedure is used when $N$ tests are performed in sequence. For each test $n \in \{1, ..., N\}$, a test statistic $...
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intention to treat needed for a sub-analysis of RCT

After running the main analysis with ITT setting for a longitudinal RCT, we want to do a sub-analysis focusing on the treatment group only, do we still need to report the ITT analysis results? In the ...
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Calculating doses using Continual Reassessment Method

Having trouble with this problem. Doesn't seem too difficult but can't find the easiest way to set up equations to solve it. We are given beta distribution toxicity level and starting dose. PROBLEM We ...
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Sample size calculation for a Randomised Controlled Trial

I know the sample size calculations for a Randomised Controlled Clinical Trial for inferiority, superiority and non-inferiority setups. But, say I have a Cross-over Randomised trial design with one ...
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Pooling Profile Penalised LTRs in multiple imputation

I am analysizing data from a clinical trial. I used multiple imputation to impute the (binary) outcome variable, which is the only variable with missing data. All of the covariates are categorical and ...
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Period effect in crossover design

I am confused with period effect, secular change, temporal trends in crossover design. In this article it is stated that The randomization of the treatment sequence helps to account for temporal ...
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Choose statistical test method: comparing the frequency of a disease (only interested the disease post-procedure) in 2 groups of patients

I am working on 2 groups of patients, group A and group B. The patients in both groups have received a same procedure. We have observed the patients before and after the procedure. Suppose there is a ...
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R: Sample size calculation for Logrank (survival test)

I have two groups of mice with tumors: a group treated and a group untreated. We know that after 4 weeks, the survival rate will be: 0% survival for the untreated mice (or 100% death rate) (we expect)...
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Analysis of ordinal patient data across 3 time points (ordinal regression vs. Wilcoxin rank sum)?

I am conducting a study of a number of patients with a disease, and using an ordinal scale assessment of functional status at 3 different time points. In this example we can say that I have 100 ...
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intention to treat with missing outcomes in longitudinal data

In an ITT randomized trial, there are one baseline response (y0) and 5 post-treatment follow-ups (y1...y5). Although the number of post-treatment follow-ups is predetermined, participants can drop out ...
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Sample size calculation in a clinical trial

I'm doing a clinical trial and I'm comparing a certain number before treatment and after treatment. I recorded the numbers for each patient before treatment and after treatment and take the difference(...
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Significance Test for Multiple Categorical Variables, Race and Clinical Trial Type

Dataset: approximately 800 patients from one hospital over 5 years that enrolled into a clinical trial. Variables include race/ethnicity, zip code, and the type of trial they enrolled into (coded as &...
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Sample size for a comparison of means based on rates

In a clinical trial, I want to demonstrate an effect following an intervention between two groups. The outcome variable is the rate of improvement. That is, the patient may experience an improvement (...
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Estimate the sample size in cross sectional study when the required sample size larger than the population in a small city

I would like to know how to estimate the sample size in the cross-sectional study when the required sample size is larger than the population on Prevalence of vitamin Deficiency in multiple sclerosis ...
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Example of multiple comparisons problem

Pharma companies can get FDA approvals on multiple indications for a single drug, e.g. different kinds of cancers. I was reading about the multiple comparisons problem, i.e. an effective inflation of ...
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How to find how big is the difference between three groups with 95% confidence interval [closed]

I have three treatment groups and one score variable (dependent variable) and the data is not normal. Hence, I performed the Kruskal Wallis test to find the hypothesis. The result is there is a ...
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Sample size calculation for a non-inferiority RCT

I am planning to test the non-inferiority of a new resistance training program compared to the standard training program. The primary outcome will be maximal muscle strength that will be measured pre ...
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2 votes
1 answer
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How trustworthy are biomarker estimates and conclusions in this covid vaccine paper?

My question is about the Correlates of protection against symptomatic and asymptomatic SARS-CoV-2 infection paper from the developers of the ChAdOx1/Vaxzevria vaccine. The paper establishes ...
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Re-constructing regression coefficients from subgroup analysis results from randomized clinical trials

I'm looking at a common situation in medical research, where only aggregate results get published, but we'd really like to get information that is not directly provided. For a randomized controlled ...
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2x2 Crossover Trial - minimum observations to run a linear mixed model

I am planning a 2x2 randomized crossover trial with about 20-25 subjects. There will be one measurement (continuous outcome) with period A (intervention) and period B (placebo) for each individual. ...
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Time zero for a switch target trial

One of the most difficult aspects in target trial emulation in my opinion is the time zero specification. Let's say I am interested in emulating a hypothetical target trial in which patients who ...
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Randomized controlled trial and DAG

In a DAG, why does a randomized controlled trial ensure there are no backdoor paths from treatment to response and hence no omitted variable bias?
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Can the variance of my posterior distribution reflect the amount of missing data from my sample?

I have treatment and outcome data (both binary, 100 samples) from two exchangeable populations which I'd like to contrast. The outcome data is partially missing, which was anticipated. Furthermore, ...
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Appropriate model choice for analyzing many repeated measurements in the context of a parallel arm randomized controlled trial

Background I am conducting a parallel-arm randomized controlled trial comparing Treatment A against a Control. Each week for 10 weeks I measure anxiety in each group each week (giving a total of 10 ...
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Can I pool together data from two seperate RCTs of the same intervention when I have access to both datasets? If so, what analysis is appropriate?

Background I have available the data from: A parallel arm RCT of Intervention A compared to a control group that was conducted several years ago. The primary outcome is a difference in the post-...
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3 votes
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What is censoring distribution and how to get it from accruing period, follow-up period and stopping time of trial?

I am reading Dirk Moore's Applied Survival Analysis 11.8 Example 11.1 on page 173. The book is trying to simulate power of logrank test. I cannot see the book's conclusion on censoring distribution. ...
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Is trial with accrual period left truncated?

I am reading Dirk Moore's Applied Survival Analysis 11.2. "...However, patients actually enter over an accrual period of length a, and then, after accrual to the trial has ended, they are ...
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Using change scores of one variable to predict change scores of another variable

I have data from a pre-post RCT that considered multiple secondary outcomes of various types (e.g. psychological, diet-related, sleep-related). I want to know whether the magnitude of change in one of ...
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Biostatistics book suggestion

I am a statistical programmer and am working on SAS in a pharma company. Also I have masters in statistics and have interest in the subject. Can anyone suggest me books on biostatistics, helps in SAS ...

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