International Journal of Applied Science and Technology

ISSN 2221-0997 (Print), 2221-1004 (Online) 10.30845/ijast

Determination of the Best Probability Plotting Position for Predicting Parameters of the Weibull Distribution
Ahmad Shukri Yahaya, Chong Suat Yee, Nor Azam Ramli, Fauziah Ahmad

Abstract
Probability plotting position methods was compared to estimate the shape and scale parameters of the Weibull distributions. Simulation technique was used to obtain random variables for twelve different Weibull distributions. Ten probability plotting positions were compared namely Hazen, California, Weibull, Blom, Gringorten, Chegodayev, Cunnane, Tukey, Beard and Median formulas. To determine the best probability plotting positions, three error measures were used which are the normalized absolute error, mean absolute error and the root mean square error. This study shows that the Gringorten formula performs the best for all sample sizes.

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