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The purpose of this paper is to provide further study of the Marshall–Olkin log-logistic model that was first described by Gui (Appl Math Sci 7:3947–3961, 2013). This model is both useful and practical in areas such as reliability and life testing. Some statistical and reliability properties of this model are presented including moments, reversed hazard rate and mean residual life functions, among others. Maximum likelihood estimation of the parameters of the model is discussed. Finally, a real data set is analyzed and it is observed that the presented model provides a better fit than the log-logistic model.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-2007-x) contains supplementary material, which is available to authorized users.

Aim of study: To investigate the successful rate for Endo crowns done by Saudi doctors. Materials and Methods: survey study contain explanatory questions about the problems of Endo crowns may doctor face it, collected from sample size 100 of Dental Senior, Intern and specialties, the data was subjected to statistical analysis using SPSS version 19. Descriptive as well as inferential statistics were done including frequencies, mean and Chi square test with the value of significance kept under 0.05. Results: our result showed that there is statistically significant increase of successful rate of endo crowns depends on the survey questions. Conclusions: Within the limits of this study it can show the efficiency of Endo crowns.