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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How to correctly calculate the type I error in a two-step clinical trial when stopping after the first step?

I just finished reading the following article by Berger & Berry (1988) in which they explain how subjectivity enters statistical analyses. One of their examples concerns a clinical trial with ...
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13 views

Should one adjust analyses if interim analysis is planned for an outcome other than the primary outcome?

It is widely accepted that analyses of clinical trials have to be adjusted if interim analyses are planned in order to decide if early termination is necessary due to evidence for superiority of one ...
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25 views

Diagnostic device hypothesis testing for superiority to a fixed value

I am designing a study to demonstrate that a diagnostic medical device is more sensitive than a fixed performance goal of 70%. Currently I am attempting to determine the appropriate sample size. My ...
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15 views

Null hypothesis for carry-over effect

I am looking to test a null hypothesis that there is no carry-over effect in cross-over trials. Where: I understand that the null hypothesis will be C/O effect A = C/O effect B = 0, however I am ...
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16 views

Ordered categorical variable descriptive statistics

I'm writing a report on a (fictional) randomised controlled trial, and I'm working on my first table, baseline characteristics. It's going to look more or less like this: (The values are approximate,...
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17 views

Is my RCT a cluster randomized trial with 'person-level outcomes' or 'cluster-level outcomes'?

I am going to conduct a study in a slum area with 94 catchments (clusters). They are randomly assigned one of two treatments, and then within those catchments, 10 women are randomly chosen for ...
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87 views

Comparing two or more treatments with inverse probablity of treatment weighting

I am working on a cardiovascular observational study featuring three or more competing treatments. My preference would be to conduct the analysis first using 1:1 propensity score matching, for ...
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90 views

Statistical rationale for a 3+3 design

I am starting to learn about design of experiments for clinical trials and in particular I am interested in understanding the statistical rationale for the 3+3 design used for dose escalation in Phase ...
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20 views

Type of study without groups

In a randomised control trial, true randomisation is applied to decide which subjects receive treatment. In quasi experimental trial, the randomisation is only approximate. What is the name given to ...
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9 views

3-arm RCT with black vs white comparisons

I am trying to design a 3-arm randomized controlled trial - intervention A for group 1, intervention A+ B for group 2 and control group for group 3. I would also like to look for black vs white impact ...
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36 views

Need the formula and to understand the number needed to treat

I am reading the article http://www.ncbi.nlm.nih.gov/pubmed/16214598. I am having trouble with the calculation formula (to test it / reproduce it). The relevant information is in page 1282. For those ...
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41 views

Basic & quick question about confidence interval (novice)

I'm writing a research proposal and I need to include an estimation of what kind of sample size would be adequate. I've used a calculator, and I get the result that with a 95% confidence interval and ...
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11 views

Power calculation for assessing relatively success two different predictors on a continuous outcome, Fisher r-to-z?

I'm thinking about a study where I assess the relatively predictive power of two different measures. Let's say a patient comes to a clinic on 3 different days, and 3 different measures of a noisy ...
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51 views

Difference in Group Sample Rate, not Size, based on Independent Variable

I'm working on a study that involves measuring breathing effort of an individual over short periods of time (specifically breath distention). The dependent variable is based on a new therapeutic and ...
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18 views

Sample Properties for Estimation

Newbie here. I want to estimate the nationality of a person from the nationalities of his family. I am looking for ideas/pointers for the following: How can I know if his family is a good sample ...
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69 views

How to get event hazard rates from a survfit object for sample size calculation

I want to calculate the sample size for a clinical trial (right-censored time to event data). I have data of a retrospective analysis and would like to use nSurv ...
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30 views

Why does the often quoted formula for the Flemming O'Brien alpha spending function produce 'probabilities' close to 2?

Demets and Lan, STATISTICS IN MEDICINE, VOL. 13. 1341-1352 (1994), introduce the alpha-spending approach to interim analyses of clinical trials. Concretely, they introduce the idea of choosing a ...
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12 views

why best not worst overall response is used as an endpoint in clinical trials?

Best overall response is usually defined as best timepoint response designation up to progression or subsequent therapy. I wonder why best not WORST overall response is used as an endpoint in clinical ...
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24 views

Placebo effect in randomized controlled trials (RCTs)

How does the number of intervention arms in a given RCT comparing several interventions to a placebo affect the placebo effect?
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22 views

Sample Size for Non-inferiority with interim analyses (group sequential) study

I would be grateful if you could help me with calculations of sample size if I have following data: Outcome is binary (Yes/No), main hypothesis is "non-inferiority"; There are two planned analyses (...
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46 views

Best practice when analysing repeated measures (longitudinal) pre-post treatment-control designs

[Note, I am trying to extend the advice from Best practice when analysing pre-post treatment-control designs to my own situation] I have the following common design: 100 participants are randomly ...
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22 views

Adjust for covariables even in randomized experiments?

Randomization does not guarantee balance in an experiment. Balance is the prerequisite for causality, so theres a potential for using regression adjustment in randomized experiments. This is somewhat ...
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16 views

Can I still call the study placebo controlled if I give the control treatment to the test population as well

I am studying the efficacy of a novel drug in treating a cardiovascular disease with continuous variable results being measured and statistically analyzed. Suppose the control population is getting ...
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155 views

Adjustable sample size in clinical trial

Most clinical trials I see have a fixed sample size. In some cases they have prior data that allows estimating the effect size and the variance or distribution of values, and calculate the sample ...
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23 views

Analysis of PValues Matrix

in clinical environment I'm setting up a model to identify fraudolent behaviours from specific sites, calculating for each site some aspects that could lead to a p-value (this approach is based on a ...
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31 views

Analysis of pre-post data when 2 treatments given serially to same subjects

I have following data from a cross-over trial where subjects were given 2 types of treatments separated by a washout period. For each treatment measurement was made in pre and post treatment period. I ...
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1answer
87 views

How to scale up mean/variance and confidence interval of clinical trial for whole population

In a clinical trial I have 1000 patients with disease A. Their mean treatment cost is 1000$ per patient with a 95% confidence interval of [900;1100] for example. The whole population of country X is ...
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71 views

Per-protocol analysis in a clinical trial

I am doing data analysis on a clinical trial. I know the rule here is to do analysis according to intention to treat (ITT, ie. analyse according to the group to which the individuals were randomised). ...
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61 views

Regression analysis for a clinical trial with repeated measures

I am currently working with a dataset that was collected from a depression study at baseline and 6 months for a group of 60 participants. Also these participants are divided into 4 groups based on ...
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28 views

Time to event with a discrete number of time points

I'm planning a clinical study, in which my desired primary outcome is time to event. My new treatment is non-inferior to the current one in it's therapeutic abilities, however it makes an impact much ...
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19 views

Interim analysis and CI

A trial was planned and designed to be a single arm trial (one group), and the sample size was calculating using a confidence interval to achieve some accuracy in the estimation of the unknown ...
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16 views

Expected p-values from a series of trials

I'm looking at this toxicology study (http://www.sciencedirect.com/science/article/pii/S0041008X1500085X). The study has a negative control group, a positive control group and three treatment groups ...
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176 views

Change scores as outcome measurements in clinical trials

I am performing a Meta-Analysis about a mental disease, comparing intervention vs. control groups and try to extract outcome results from published study papers. In some clinical randomised trials ...
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22 views

Test that does not based on sufficient statistics [closed]

In the context of adaptive clinical trials, inverse normal method/test was addressed as not based on sufficient statistics, while sequential tests do. Is it because in adaptive design, the test is not ...
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21 views

Permuted block design Wilcoxon sum rank test

I need to do a Wilcoxon rank sum statistic for some data with a permuted-block with 2 blocks of size 6. However, I'm confused how we deal with the permuted-block randomization. My book says When ...
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109 views

Power analysis for logistic regression

I have to deliver a statistical analysis plan that will have to be approved by an ethic commettee before I could start a clinical trial. I usually deal with different kinds of tests, whose power ...
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50 views

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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63 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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26 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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1answer
81 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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31 views

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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1answer
124 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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120 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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130 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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77 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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79 views

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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1answer
26 views

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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200 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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84 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 ...
5
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1answer
191 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. ...