How to handle conservativeness of Exact p-value?

Posted by Ashwini Joshi

Sep 18, 2017 7:38:45 AM

 

By Ashwini Joshi

For small sample data or rare events data, exact non-parametric tests perform better than asymptotic tests. But they come with the disadvantage of conservativeness. Many corrections have been suggested to reduce this conservativeness but none of them solve the problems entirely.  StatXact provides various methods of computing exact p-values. Depending upon the problem at...

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Topics: biostatistics, p value, StatXact, exact statistics, Small Sample Sparse Data, Exact Tests


How to Reduce Bias in the Estimates of Count Data Regression

Posted by Cytel

Oct 29, 2015 4:00:00 PM

A common challenge of working with small sample sizes is determining proper bias correction methods when evaluating a given set of data. Oftentimes, statisticians depend on large sample sizes to naturally correct for any bias. Small sample sizes, by contrast, require innovations like Firth’s famous bias correction method.

Recently, Cytel statisticians Ashwini Joshi and Sumit Singh gave a talk...

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Topics: Access to Slides PDF, Small Sample Sparse Data


3 Statistical Challenges for Pooling Phase 1 Data

Posted by Esha Senchaudhuri

Oct 19, 2015 5:15:40 PM

It is often necessary to pool safety data from late phase studies, in preparation for regulatory submission. Some of our clients have also begun to add Phase 1 safety data to this pool. On some occasions this is required by regulators. In many cases, however, these Phase 1 data simply provide further evidence that a new therapeutic lives up to the promise of safety across patient populations.

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Topics: Data Management, Safety, Early Phase Trials, Small Sample Sparse Data


3 Strategies to Combat Inferential Conservatism in Small Sample Sizes

Posted by Cytel

Jun 25, 2015 4:28:00 PM

When conducting a clinical trial with small or sparse data sets, statistical methods meant for large sample sizes may fail to obtain an accurate interpretation of data. This is where computationally challenging exact methods often come into play.

Exact methods, however, are inferentially conservative in the sense that due to small sample sizes, the actual Type 1 error rate is often smaller...

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Topics: Sample Size, Exact Inference, exact statistics, Small Sample Sparse Data


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