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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Type-1 Error of the Two-Stage Design

Background on Two-Stage Designs In clinical trials, we are often interested in the response rate $p$ for an experimental treatment. In a typical trial, we might expose $n$ patients to the treatment ...
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power for estimating treatment heterogeneity in RCT

Could someone point me to a good resource for estimating power for detecting treatment heterogeneity via interactions in MR? Let's assume that individuals will be randomized to two study arms. To ...
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A clinical test incorrectly identified 50/150 false positives and 23/150 false negatives.Calculate the number of true positives and true negatives

Was wondering if anybody could explain how I can calculate the answer. Would be much appreciated.
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64 views

Linear Mixed Model for Longitudinal Data: Continuous vs. Discrete Time Parameter

I would like to conduct a power analysis for a linear mixed model with fixed effects for Treatment (two levels) and Time (four ...
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29 views

Power Calculation - Calculation of Absolute Difference

I've been asked to undertake a power calculation because the regular statistician is not available. I am calculating power for a trial where the endpoint will be a percentage of patients not ...
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54 views

Statistical tests for comparing a skewed clinical sample

I recently surveyed 350 low-income families -- they were randomly split into two groups: control and treatment. One of the variables I am very interested in is the amount of savings of each family. ...
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How does missing data affect analysis of clinical trials?

I was helping a friend with some problems for a clinical trials administrations course they are taking, most of it was simple statistics the last question was a little more tricky. We got the answer ...
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Randomisation for 2 site clinical study

If I want to conduct a randomised study in 2 sites comparing two clinical treatment arms, and every site is expected to include 60-80 patients, is it acceptable to randomise every new patient with ...
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75 views

Clinical trials significance

I have been a studying high energy physics (HEP) for the last few years but I recently started working on a project in medical imaging. I have been a little surprised (not entirely I was aware that ...
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119 views

Can I use bootstrapping to evaluate the effectiveness of a clinical intervention on a small sample?

I am doing an MSc in occupational therapy, which is concerned with evaluating how effective an occupational therapy intervention is on increasing individual's with learning disabilities daily living ...
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43 views

What is the best non-parametric test for ratio, two-sample clinical trial data?

Clinical trials are a field I am quite interested in and since I have trouble accepting that every clinical trial's data will follow a normal distribution with sufficient sample size I was curious as ...
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70 views

Dealing with dropping non-responders in clinical trials

I'm wondering what are some good approaches for analyzing trials where non-responders are dropped out at some set point. This is not my field, so I may be unaware of standard things! Let's say there ...
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38 views

Estimating absolute difference between two conditions

A clinical trial examines the effect of two treatments upon lung function. Patients in each group contribute data at baseline and at the end of the trial. Baseline data are provided for each group ...
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156 views

Hypothesis testing with a response scale of “1, 2, 3, 4, or not applicable”

Let's imagine I'm testing a new drug that purports to reduce the effect of a hangover when the drug is administered shortly before an episode of heavy drinking. On Friday night, I stake out the ...
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48 views

Methods for randomly allocating people between active and placebo in clinical trials

I'm looking for a way to allocate people to either group A or B. Data for the study group has 3 main variables: Age 65-90 Male or Female APOE + or APOE – (this is a blood test) I ...
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65 views

stepped wedge and additive intervention effects

Let's say we want to randomize 400 caregivers to a parenting intervention or a wait-list control group. But we also want to look at a program variation for a sub-sample of caregivers of children with ...
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210 views

Rolling out trial in phases, but not stepped wedge

Update (Sept 10, 2013): I believe it would be more correct to say that increasing baseline or endline measurements are ways to decrease the design effect, thereby making the SW design efficient, ...
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445 views

Linear regression sample size advice

I'm involved in sample size calculation for an oncology clinical trial. Our Primary outcome is quality of life (quantitative, normal). There are two treatment regimes. Therefore I started with a ...
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89 views

Backing out the standard deviation from information on baseline mean/s.d., and coefficient mean/s.d

I am trying to run a power calculation for a randomized control trial. For this I need a mean and standard deviation for our 'baseline'. There are papers out there which would have a mean and standard ...
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154 views

How to calculate the population survival probability in a two stage randomized clinical trial?

I am trying to reproduce a paper on two stage randomized clinical trials. In these clinical trials, a patient is randomized to either of the maintenance therapies $B_1$ or $B_2$ upon their remission ...
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173 views

Book recommendations for biostatisticians in CRO and pharmacy

I would like to learn more about the work and statistical methods performed as biostatistician in pharmaceutical companies and clinical research organizations. It seems the book "Essential Medical ...
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121 views

Best practice when analysing placebo-controlled within-subject designs (cross-over trial)

I would like to analyse data from a placebo-controlled within-subject design. For every subject a numeric outcome variable (Y) was measured twice - once following administration of a drug and once ...
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141 views

Normalizing when doing count statistics of patient numbers on different arms of a clinical trial

I'm looking at clinical trial data where there are various numbers of patients on different arms (A, B, C, D). All arms receive a drug that is known to cause a toxicity, but some arms receive an ...
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1answer
345 views

Interpretation of results in non-inferiority study

I need some help interpreting some results from a non-inferiority study. The primary endpoint for assessment of non-inferiority is the change from baseline in Power of Attention Score. The study is ...
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69 views

Books on designing clinical trials for psychotherapy research

I'm designing a clinical trial that will evaluate a behavioral therapy against a control condition, and I'm looking for some good texts on this topic. There are a lot of books on clinical trials in ...
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3k views

Repeated measures ANOVA for two different groups

I have conducted a clinical trial using two groups with two different treatment modalities. I have measured different physical and biochemical parameters (e.g pulse, systolic blood pressure, serum ...
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625 views

How to calculate sensitivity, specificity, and odds ratio?

I am trying to calculate sensitivity, specificity, and odds ratio of a data set, they are numerical values of percentages from 0% to 100%. How should I do the calculation? Wikipedia has the formula: ...
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How to construct a 95% confidence interval of the difference between medians?

My problem: parallel group randomized trial having a very right-skewed distribution of the primary outcome. I do not want to assume normality and use normal-based 95% CIs (i.e. using 1.96 X SE). I am ...
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403 views

Sample size for clinical trials, when effect size is predicted

How should I calculate sample size for a clinical trial when I need a power of 80% and I predict an effect size to be at lest 0.5? do I need to estimate the mean of outcome as well?
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Clinical trial design

I have a clinical trial phase 2 3 stage that I need a design for: 3 groups of 12 blood transfusion done at different Hemoglobin levels. It is not a dose escalation study because the transfusion is the ...
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Objections to randomization

In Clinical trials - a methodologic perspective, Steven Piantadosi writes (ch.13, p. 334): In Chapter 2, I noted the objections to randomization by Abel and Koch (1997) and Urbach (1993), and ...
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3k views

Where to find raw data about clinical trials?

I wish to use raw data about clinical trials for the end year examination of my master students. These data could deal with any kind of molecule as long as the trials were complete (Phase 1 to 4). Do ...
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225 views

How should one control for group and individual differences in pre-treatment scores in a randomised controlled trial?

Andrew Gelman, in the book he wrote with Jennifer Hill, states in Chapter 9, (section 9.3), on page 177: It is only appropriate to control for pre-treatment predictors, or, more generally, ...
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372 views

How does the size of a dataset affect confounding in both randomised trials and observational studies?

I have heard that larger sample sizes in randomised trials lead to a smaller possibility of confounding. Why is this true in the case of randomised trials? Also, how does sample size of an ...
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319 views

When using stratified randomization in a RCT, how many envelopes per stratum should be prepared?

If one considers a hypothetical RCT, say a total sample size of 300, separated into three strata based on surgical procedure (open surgery, closed surgery, or combined procedure). Blocking in groups ...
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57 views

Correlating various diagnoses with amount of weight gained

I have a processed dataset where patients took a medication and gained a varying amount of weight. In addition, any ICD9 diagnoses the patients have received while being monitored are recorded. I'd ...
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124 views

Analyzing treatment effect with possibly flawed control data

I've got some rather messy data from a natural experiment. A number of subjects were measured (the measurements were hopefully-Poisson distributed counts and associated offsets), placed on a ...
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104 views

Pre and Post, treated and un treated but from same subject

A treatment was given to one hand of a subject, and a single outcome metric is measured for both hands, twice pre and several times post treatment. What is best practice for assessing effectiveness ...
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909 views

How to extract data from published articles (RCTs) to do a meta-analysis?

I am doing a meta analysis for the first time and have a few basic questions regarding statistical analysis. Let's say I have one study where the primary outcome (thrombosis) in the 2 treatment ...
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868 views

Covariate Adjusted Logistic Regression (“Adjusted Analysis”)

I am trying to find some help with something that is called an "Adjusted Analysis" (or also Covariate Adjusted Logistic Regression); a typical response has been that I might just want multivariable ...
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330 views

How to handle multiple comparisons in a three-arm clinical trial?

I have 3 arms in a trial. I want to compare results of a survey before during and on completion of a treatment. Data is not normally distributed. What test should I use?
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177 views

Does significance test make sense to compare randomised groups at baseline?

Many randomised controlled trial (RCT) papers report significance tests on baseline parameters just after/before randomisation to show that the groups are indeed similar. This is often part of a ...
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When is a randomised controlled trial (RCT) balanced?

I believe that for ANOVA unbalanced means unequal groups. But for randomised controlled trials unbalanced seems to mean something like groups of different characteristics despite randomisation. So in ...
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Why is bias affected when a clinical trial is terminated at an early stage?

An interim analysis is an analysis of the data at one or more time points prior the official close of the study with the intention of, e.g., possibly terminating the study early. According to ...
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762 views

Overall type I error when repeatedly testing accumulating data

I have a question about group sequential methods. According to Wikipedia: In a randomized trial with two treatment groups, classical group sequential testing is used in the following manner: If n ...
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193 views

In relation to clinical trials, what is clinical reasoning in contrast to statistical reasoning?

I read Clinical Trials, a Methodologic Perspective (S. Piantadosi) as I was suggested by one of you. According to the author: A trialist must understand two different modes of thinking that ...
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841 views

Building Cox Model using forward likelihood-ratio testing - Appropriateness of adding continuous variables to model?

I am constructing Cox models that predict survival in a clinical trials cohort. After speaking to our statistician (who is away at the moment, hence this post), I was advised to take a forward ...
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132 views

Book on designing clinical trials in oncology

I would like to have a good idea on how to design clinical trials in oncology. In that issue, I am looking for a compact book that could give me a good overview, with the emphasis on statistical ...
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33k views

What is the difference between effectiveness and efficacy in determining the benefit of therapy 'A' on condition 'B'?

The context of this question is within a health framework i.e. looking at one or more therapies in the treatment of a condition. It appears that even well respected researchers confuse the terms ...
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Best practice when analysing pre-post treatment-control designs

Imagine the following common design: 100 participants are randomly allocated to either a treatment or a control group the dependent variable is numeric and measured pre- and post- treatment Three ...