Al-Saleh and Al-Kadiri first proposed double rank set sampling (DRSS). It seems that this ranked set sampling (RSS) modification can reduce the loss of RSS efficiency caused by ranking errors, and it is more effective than RSS and simple random sampling (SRS) to estimate the population mean. The proposed likelihood function is used to estimate the parameters of the three-Parameters Weibull distribution. Based on double ranked set sampling, extreme ranked set sampling, ranked set sampling (RSS) and simple random sampling (SRS) designs, the maximum likelihood estimator (MLE) is compared with the corresponding likelihood estimator. A simulation was carried out and the absolute relative biases, mean square error (MSE) and relative efficiency of different schemes were compared. It is found that, MSEs based SRS data has the largest MSEs comparing to RSS and its modifications schemes. This study revealed that DRSS technique has the superior over the rest of other sampling schemes. In almost all cases, DRSS has the smallest MSEs and largest efficiencies.
The purpose of this study was to determine the prevalence and severity of temporomandibular joint disorders among postgraduate students at Egyptian universities. Materials and methods: 840 postgraduate students from different Egyptian universities were recruited and answered Fonseca's questionnaire. Out of the 840 respondents, 593 were included and evaluated using Fonseca's anamnestic index to classify them according to the severity of the disorder. Results: The prevalence of temporomandibular disorders among the included population was 73.4%. The most common degree of severity reported was the mild category being 57% followed by moderate (31.7%) then severe (11.3%). Temporomandibular disorders were prevalent among females with a frequency of 73.3% while 26.7% for males. There was significant association between the temporomandibular disorders and sex (P<.001). Conclusion: There's high prevalence of temporomandibular disorders among Egyptian postgraduate students. There's an association between sex and prevalence of temporomandibular disorders, with females being more susceptible to the development of temporomandibular disorders.
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