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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Why is screening test more concerned about sensitivity while diagnostic test is more concerned about specificity?

Screening Test : A large number of apparently healthy people are tested to identify those who are at a risk of the condition or disease. ...
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Randomization for multi-site clinical trial, screen failures

Two questions about appropriate randomization procedures for a small two-armed trial at 3 sites. About 100 participants total, evenly split between study arms. First, we are concurrently enrolling ...
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27 views

Sample size calculation for clinical trial

I am facing a problem regarding sample size calculation of clinical trial. Currently a drug is used at 2.5 mg for adult and ...
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25 views

Can we say a control / placebo group exists in a complex intervention?

In the case of something like acupuncture (as an example), it is very hard to set a placebo group or control group, since this therapy is not like taking drugs. Lets say if the needle is not in the ...
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64 views

ANOVA or ANCOVA

I have to analyze a study where 2 treatments (t1 and t2) were used to control blood sugar levels. The 't2' is a new treatment which is being compared with an old established treatment 't1'. I have a ...
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Classification with two different dataset

I am working on a cancer classification model.Task is ,I am initially given a data set of 500 people and 1000 features.These people are given some kind of treatment(say Treatment 1). Some people are ...
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39 views

Randomization software/service for clinical trial

I need a software/web-based system for the clinical randomization. This software/service should have the capabilities for handling stratification, multiple centers and block. The sample size of ...
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49 views

RCT baseline controls that do not match outcome measures

Does anyone have any input on whether it is ok to use baseline measures as control variables in a randomized controlled trial (RCT) if they are not exactly the same as the outcome measures? I.e., if ...
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93 views

Bayesian inference of a clinical trial for clinicians

I am a clinician who is more adept than average at interpreting clinical trials in a frequentist manner. At this point, interpreting a trial as a frequentist has kind of become a procedure: check ...
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27 views

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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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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52 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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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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27 views

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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83 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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133 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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83 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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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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194 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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64 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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77 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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320 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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648 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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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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198 views

Power calculation for cluster-level analysis in cluster randomized trials

I would like to solve for $\pi_1$ in equation 7.14 of Hayes and Moulton's "Cluster Randomized Trials". I can't for the life of me remember how to do so. Here is a link to the equation. Here is the R ...
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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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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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151 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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154 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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420 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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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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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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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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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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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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249 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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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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380 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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59 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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127 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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106 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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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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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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338 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?