Ehab F. Abd-Elfattah

Bio: Ehab F. Abd-Elfattah is an academic researcher from Ain Shams University. The author has contributed to research in topics: Confidence interval & Distribution (mathematics). The author has an hindex of 5, co-authored 22 publications receiving 97 citations. Previous affiliations of Ehab F. Abd-Elfattah include Taibah University.

The weighted log-rank class of permutation tests: P-values and confidence intervals using saddlepoint methods

Abstract: Test statistics from the weighted log-rank class are commonly used to compare treatment with control when there is right censoring. This paper uses saddlepoint methods to determine mid-p-values from the null permutation distributions of tests from the weighted log-rank class. Analytical saddlepoint computations replace the permutation simulations and provide mid-p-values that are virtually exact for all practical purposes. The speed of these saddlepoint computations makes it practicable to invert the weighted log-rank tests to determine nominal 95% confidence intervals for the treatment effect with right-censored data. Such analytical inversions lead to permutation confidence intervals that are easily computed and virtually identical to the exact intervals that would normally require massive amounts of simulation.

Log-rank permutation tests for trend: saddlepoint p-values and survival rate confidence intervals

Abstract: Suppose p + 1 experimental groups correspond to increasing dose levels of a treatment and all groups are subject to right censoring. In such instances, permutation tests for trend can be performed based on statistics derived from the weighted log-rank class. This article uses saddlepoint methods to determine the mid-P-values for such permutation tests for any test statistic in the weighted log-rank class. Permutation sim- ulations are replaced by analytical saddlepoint computations which provide extremely accurate mid-P-values that are exact for most practical purposes and almost always more accurate than normal approximations. The speed of mid-P-value computation allows for the inversion of such tests to determine confidence intervals for the percentage increase in mean (or median) survival time per unit increase in dosage. The Canadian

The weighted log-rank class under truncated binomial design: saddlepoint p-values and confidence intervals

Abstract: The randomization design used to collect the data provides basis for the exact distributions of the permutation tests. The truncated binomial design is one of the commonly used designs for forcing balance in clinical trials to eliminate experimental bias. In this article, we consider the exact distribution of the weighted log-rank class of tests for censored data under the truncated binomial design. A double saddlepoint approximation for p-values of this class is derived under the truncated binomial design. The speed and accuracy of the saddlepoint approximation over the normal asymptotic facilitate the inversion of the weighted log-rank tests to determine nominal 95% confidence intervals for treatment effect with right censored data.

Weighted log-rank tests for clustered censored data: Saddlepoint p-values and confidence intervals.

Abstract: Clustered data with censored failure times frequently arise in clinical trials and tumorigenicity studies. For such data, the common and extensively used class of two-sample tests is the weighted l...

Univariate Discrete Distributions

Abstract: Here are two books on a topic new to Technometrics: statistical and mathematical demography. The first author of Applied Mathematical Demography wrote the first two editions of this book alone. The second edition was published in 1985. Professor Keyfritz noted in the Preface (p. vii) that at age 90 he had no interest in doing another edition; however, the publisher encouraged him to find a coauthor. The result is an additional focus for the book in the world of biology that makes it much more relevant for the sciences. The book is now part of the publisher’s series on Statistics for Biology and Health. Much of it, of course, focuses on the many aspects of human populations. The new material focuses on mature population models, the particular focus of the new author (see, e.g., Caswell 2000). As one might expect from a book that was originally written in the 1970s, it does not include a lot of information on statistical computing. The new book by Alho and Spencer is focused on putting a better emphasis on statistics in the discipline of demography (Preface, p. vii). It is part of the publisher’s Series in Statistics. The authors are both statisticians, so the focus is on statistics as used for demographic problems. The authors are targeting human applications, so their perspective on science does not extend any further than epidemiology. The book actually strikes a good balance between statistical tools and demographic applications. The authors use the first two chapters to teach statisticians about the concepts of demography. The next four chapters are very similar to the statistics content found in introductory books on survival analysis, such as the recent book by Kleinbaum and Klein (2005), reported by Ziegel (2006). The next three chapters are focused on various aspects of forecasting demographic rates. The book concludes with chapters focusing on three areas of applications: errors in census numbers, financial applications, and small-area estimates.

Nonparametrics Statistical Methods Based On Ranks

Abstract: Thank you very much for reading nonparametrics statistical methods based on ranks. Maybe you have knowledge that, people have look hundreds times for their favorite novels like this nonparametrics statistical methods based on ranks, but end up in harmful downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they are facing with some malicious virus inside their desktop computer.

What a performance

Abstract: The recent appearance of the annual reports of most publicly quoted petroleum companies for the financial year 2003, together with Shell having to substantially downgrade its proven reserves, makes it a timely moment to consider 2003 performance for a range of petroleum companies, writes David Wood.