Mohamed Ismail Mohamed Hamdy

Hamdy, M. I., and Al-Ibrahim, A. H.

01/01/2003

A Descriptive Study of the Academic Status of the Students Admitted to Qatar University during 1995-2000,' Research Report, Qatar University.

Mohamed Ismail Mohamed Hamdy

Hamdy, M. I.

01/01/1995

Mohamed Ismail Mohamed Hamdy

Hamdy, M. I., El-Bassiouni, M. Y.

01/03/1993

Halperin et al. (1988) suggested an approach which allows for k Type I errors while using Scheffe's method of multiple comparisons for linear combinations of p means. In this paper we apply the same type of error control to Tukey's method of multiple pairwise comparisons. In fact, the variant of the Tukey (1953) approach discussed here defines the error control objective as assuring with a specified probability that at most one out of the p(p-l)/2 comparisons between all pairs of the treatment means is significant in two-sided tests when an overall null hypothesis (all p means are equal) is true or, from a confidence interval point of view, that at most one of a set of simultaneous confidence intervals for all of the pairwise differences of the treatment means is incorrect. The formulae which yield the critical values needed to carry out this new procedure are derived and the critical values are tabulated. A Monte Carlo study was conducted and several tables are presented to demonstrate the experimentwise Type I error rates and the gains in power furnished by the proposed procedure

Mohamed Ismail Mohamed Hamdy

Hamdy, M. I., El-Bassiouni, M. Y.

01/01/1993

Mohamed Ismail Mohamed Hamdy

Hamdy, M. I., Atalla, M. A.

01/10/1991

Mohamed Ismail Mohamed Hamdy

Halperin, M., Hamdy, M. I., and Thall, P. F.

01/08/1989

Halperin, Gilbert, and Lachin (1987, Biometrics 43, 71-80) obtain confidence intervals for Pr(X less than Y) based on the two-sample Wilcoxon statistic for continuous data. Their approach is applied here to ordered categorical data and right-censored continuous data, using the generalization zeta = Pr(X less than Y) + 1/2Pr(X = Y) to account for ties. Deviations from nominal coverage probability for various sample sizes and values of zeta are obtained via simulation of either three or six ordered categories based on underlying Poisson or exponential distributions. The simulation results indicate that the proposed method performs quite well, and it is apparently superior to the approach of Hochberg (1981, Communications in Statistics--Theory and Methods A10, 1719-1732) for values of zeta far from 1/2

Mohamed Ismail Mohamed Hamdy

Halperin, M., Lan, K. K. G., and Hamdy, M. I.

01/06/1988

An approach to multiple comparisons defines the error control objective as assuring with given probability that k or fewer out of N specified linear combinations of p means are significant when an overall null hypothesis is true, or that k or fewer confidence interval statements are incorrect. The case fc = 0 is basically the Scheffe (1953) method except for the consideration of a specified set of N linear combinations rather than all possible linear combinations. A theoretical result is obtained under normal theory and we assume an infinite number of linear combinations with normalized coefficients, that is the sum of squares is unity, uniformly distributed over the unit p-sphere. For a finite number N of specified linear combinations the problem is reformulated in a way which in principle would allow computation of the exact distributions required to provide critical values. In general, the computations required are so complex that they are impractical, but a Monte Carlo approach is straightforward.

Mohamed Ismail Mohamed Hamdy

Hamdy, M. I.

Distribution-Free Three- Sample Test for Detecting Trend in the Pure Location Model,'

Mohamed Ismail Mohamed Hamdy

Hamdy, M. I.

A Recursive Formula to Compute the Mean of the Non-central Hypergeometric Distribution,'Submitted to Environmental and Ecological Statistics (2016).