Publication Bias in Meta-Analysis: Confidence Intervals for Rosenthal's Fail-Safe Number

The purpose of the present paper is to assess the efficacy of confidence intervals for Rosenthal's fail-safe number. Although Rosenthal's estimator is highly used by researchers, its statistical properties are largely unexplored. First of all, we developed statistical theory which allowed us to produce confidence intervals for Rosenthal's fail-safe number.This was produced by discerning whether the number of studies analysed in a meta-analysis is fixed or random. Each case produces different variance estimators. For a given number of studies and a given distribution, we provided five variance estimators. Confidence intervals are examined with a normal approximation and a nonparametric bootstrap. The accuracy of the different confidence interval estimates was then tested by methods of simulation under different distributional assumptions. The half normal distribution variance estimator has the best probability coverage. Finally, we provide a table of lower confidence intervals for Rosenthal's estimator.Comment: Published in the International Scholarly Research Notices in December 201

A meta-analysis of the reliabilty of young’s internet addiction test

AIM: Currently there are at least 5 scales being used most frequently in studies for diagnosing Internet addiction or problematic Internet use. Moreover there are various studies using each scale mentioning differing reliability coefficients. The most frequently used questionnaire until now is Young’s Internet addiction test (YIAT20). The aim of this study is to produce an overall value for the reliability YIAT20, drawing from a large sample of studies. METHODS: A systematic search of the databases PsycINFO, Medline, EMBASE, Pubmed/Medline, and Google Scholar revealed 20 studies using out of which 11 gave reliability measures. We performed a meta-analysis of the values of Cronbach’s α values mentioned in each study, noted various moderates including sample subgroup (college or pre-college students), sample mean age, sample male percentage, online or offline answering of the questionnaire, and continent of the author’s study. Difference were sought between reliability in various categories while we performed a weighted least squares general linear model to find predictive factors of the variance in YIAT20’s reliability. All analyses were done in PASW 18.0. RESULTS: Eleven studies comprising of a total of 6821 participants were included in the final analysis. The overall Cronbach’s alpha computed from the studies was 0.889 (95% CI 0.884-0.895). The standard deviation of α was low: 0.049. Cronbach’s α was significantly lower in pre-college students [Mean Difference: -0.045 (95% CI-0.057, -0.032)], while Asian studies produced a higher value of Cronbach’s α not reaching significance [Mean Difference: -0.015 (95% CI-0.032, 0.002)]. The weighted least squares general linear model was adequate with R-Squared = 0.504 (Adjusted R-Squared = 0.292). The variable continent proved out to be a significant predictor of the value of reliablity. CONCLUSION: YIAT20 is a frequently used scale to measure Internet addiction. Mean differences showed that it is more reliable in college students and probably in Asia. A general linear model showed that the continent of the study affects significantly the outcome of reliability of the study with reliability decreasing when the continent is Europe. More studies are required to examine which scale is more reliable in pre-college students and in other continents

Internet addiction among Greek university students: Demographic associations with the phenomenon, using the Greek version of young's Internet addiction rest

Internet addiction (IA) is a new disorder described in 1996 by the psychologist Kimberly Young. The aim of this paper is to estimate the percentage of IA among Greek university students. Results of a sample survey among 1876 Greek university students, 18-27 years old, are presented. The questionnaire consisted of eight questions from Young's Diagnostic Test for Internet Addiction (YDTIA) as well as an inventory including demographic factors and questions about academic performance, computer and Internet use. YDTIA had a good reliability and diagnostic accuracy, tested with Cronbach's alpha (0.71) and sensitivity analysis. Results show that the percentage of IA (5-8 YDTIA criteria) is 11.6%, while problematic Internet users were (3-8 YDTIA criteria) 34.7%. Men were more likely to be addicted to the Internet than women, and Internet addicted students were associated with poorer academic performance. Multiple logistic regression showed that significant predictors of IA included increased hours of daily Internet use, increased hours visiting chat rooms, sex pages and blogs, male gender, divorced status, poor grades, and accessing the Internet outside of the home. The results of this study will allow health officials to recognise students who are Internet addicted or on the verge of becoming addicted and stress risk factors indicating a need for intervention in order to prevent the appearance of IA

Assessment of Performance of Correlation Estimates in Discrete Bivariate Distributions using Bootstrap Methodology

Little attention has been given to the correlation coefficient when data come from discrete or continuous non-normal populations. In this article, we consider the efficiency of two correlation coefficients which are from the same family, Pearson's and Spearman's estimators. Two discrete bivariate distributions were examined: the Poisson and the Negative Binomial. The comparison between these two estimators took place using classical and bootstrap techniques for the construction of confidence intervals. Thus, these techniques are also subject to comparison. Simulation studies were also used for the relative efficiency and bias of the two estimators. Pearson's estimator performed slightly better than Spearman's

Assessment of Performance of Correlation Estimates in Discrete Bivariate Distributions using Bootstrap Methodology

Little attention has been given to the correlation coefficient when data come from discrete or continuous non-normal populations. In this article, we consider the efficiency of two correlation coefficients which are from the same family, Pearson's and Spearman's estimators. Two discrete bivariate distributions were examined: the Poisson and the Negative Binomial. The comparison between these two estimators took place using classical and bootstrap techniques for the construction of confidence intervals. Thus, these techniques are also subject to comparison. Simulation studies were also used for the relative efficiency and bias of the two estimators. Pearson's estimator performed slightly better than Spearman's

On the Greek economic crisis of 2009–2012: Fundamental causes and effects; future prospects for Greece and Eurozone

The aim of this paper is to present the economic, social, political and moral causes and effects of the Greek debt crisis. The debt and deficit figures for Greece are presented. The causes of the crisis are: (a) corruption, (b) tax evasion and deposit of the stolen money in tax heavens (c) inefficiency of the public sector, (d) absence of transparency practices in the system of justice, in the areas of health, education, defense and labor, (e) excessive consumption habits of the Greeks, (f) lack of entrepreneurial and innovative spirit among the Greeks, (g) excessive debt and non-permissible budget deficit. The consequences are: (a) unemployment, (b) poverty, (c) social exclusion, (d) rising inequalities as it is shown by original research on Gini coefficient, (e) homelessness, (f) health problems, (g) rising suicide rate. Future prospects are: possible exclusion of Greece from Eurozone because of inability to repay debt and to reduce deficit

George Higoumenakis (1895-1983): Greek dermatologist

This paper describes the Higoumenakis sign, enlargement of the sternal end of the clavicle in patients with late congenital syphilis and the dermatologist after whom it is named. Several professors and doctors from the Medical School of the University of Athens opposed his actions especially at the University in Greece. His persistence led him to productive scientific activity in syphilis, leishmaniasis and psoriasis. fie became a member of the Greek Parliament from 1964 to 1967 and eventually Minister of Hygiene - even though this may have been an imprudent political choice, due to the unstable socio-political status of that period. He died on 27 December 1983 at the age of 88

Statistical investigative analysis of the factors which contribute to the productivity of the academic teachers with respect to scientific research output and teaching effectiveness

The investigation of productivity of Academic Teachers in terms of research and teaching effectiveness is a subject which has attracted considerable research and which determines the economic level and prospects of a country. In this paper we investigate the factors which influence the academic teachers’ effectiveness in the Greek Academic Institutions, either Universities or Technological Educational Institutions, with respect to their research and teaching. We have carried out two sampling surveys. In the first one, a questionnaire has been sent to 128 Professors at Greek Academic Institutions. In the second one, a questionnaire has been sent to 374 students studying at Greek Institutions of Higher Education, either Universities or Technological Educational Institutions. The Statistical Methods employed were the following: Descriptive Statistics, Chi-Square Tests and T-Tests, Linear Models, Factor Analysis and Reliability Analysis. The results are the following: A) The productivity of an academic teacher, which is defined as research output and teaching effectiveness, depends on the following factors: A1) The number of publications in internationally recognized journals, Indexed in databases with impact factor. A2) The number of citations to his papers from other authors working on similar subjects. A3) His Teaching effectiveness measured by the annual reports of evaluation by his students, A4) The type of the Academic institution where he works, A5) His educational 2 background and his studies, A6) His work previous experience. Another important result is the following: According to the answers to the questionnaire by the Academic teachers, research productivity is the principal characteristic of a productive academic, but according to the students’ answers to their questionnaire , the characteristic which is of paramount importance for an academic is his teaching effectiveness in terms of making clear the subject of his courses, his daily contact with the students, his readiness to answer questions to his students and his general attitude to improve the knowledge of his students with respect to the subject which he teaches. The Chi-Square Test has revealed a strong association between work previous experience and the following variables: research activity, rank, knowledge of foreign languages, type and principle schools affiliated to an academic institution and level of undergraduate curriculum subjects, which the professor teaches. A general conclusion is that the type of Institution, the existence of post-graduate programs and the previous work experience of the Professor determine his effectiveness as teacher and research worker