CALL) programs have been incorporated into language classrooms over the past five decades, it has become more important to find a clear answer to questions such as to what extent, and under which moderator variables CALL programs can yield more effective outcomes as compared to traditional language instruction. The present meta-analysis is a comprehensive investigation to determine the extent of the effectiveness of hypertext annotations on the learners' vocabulary learning. Moreover, the study

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... aimed at identifying the moderator variables that influence the heterogeneity of the effect of various studies. Methods: The statistical population of the present study consisted of all the studies conducted in the past related to the effectiveness of hypertext annotations on learners' vocabulary learning. To this aim, an exhaustive research of the multiple electronic databases was carried out in order to identify all the studies examining the relative effectiveness of CALL on enhancing learners' vocabulary learning The main criterion for selecting the studies to be analyzed in the present research was their publication in journals or proceedings of conferences during the period between 1950 to 2014. Concurrently, the experts in this area were also consulted for articles that had not been identified in the primary search. Eventually, the search process resulted in the identification of 132 articles of potential relevance to the present meta-analysis. In the next stage, all studies were investigated more carefully and examined based on the checklist which was the criterion for the final selection of those studies that should be included in the present meta-analysis. Finally, a total sample of 36 studies met the required criteria and selected for the final analysis. Data analysis was performed using Comprehensive Meta-analysis Software (Version 2). Findings: With respect to the overall effect size of the hypertext annotations on the students' vocabulary acquisition, the results of 36 study in the present meta-analysis rev [...]