Convenience sampling is one of the most commonly used sampling procedures in second language acquisition studies, but this non-random sampling procedure suffers from a lot of problems including the inability of controlling for initial differences between experimental and control groups. The present study tries to introduce conditions and criteria which enable researchers to account for these drawbacks and at the same time make validity claims. Individual scores and group statistics are compared with regard to a group of essential factors known to be important for the purpose of the study. The overall value calculated for essential factors is then used to make judgments about the groups' comparability. The contribution of this method to the current procedures of sampling arises from its factual accuracy which is supposed to enhance the validity of findings obtained from studies employing non-probability sampling procedures.

The present article reports the findings of a study that explored(1) whether direct written corrective feedback (CF) can help high-proficient L2 learners, who has already achieved a rather high level of accuracy in English, improve in the accurate use of two functions of English articles (the use of 'a' for first mention and 'the' for subsequent or anaphoric mentions); and (2) whether there are any differential effects in providing the two different types of direct written CF (focused and unfocused) on the accurate use of these grammatical forms by these EFL learners. In this study, sixty high-proficient L2 learners formed a control group and two experimental groups. One experimental group received focused written CF and the other experimental group received unfocused written CF, while the control group received no feedback. The statistical analyses indicated that both experimental groups did better than control group in the post-test, and moreover, focused group significantly outperformed unfocused one in terms of accurate use of definite and indefinite English articles. Overall, these results suggest that focused written CF is more effective than unfocused one, at least where English articles are concerned, in improving grammatical accuracy of high-proficient L2 writers and thus strengthens the case for teachers providing focused written CF.

This study was an attempt to compare EFL teachers' and intermediate high school students' perceptions of written corrective feedback on grammatical errors and also to specify their reasons for choosing comprehensive or selective feedback and some feedback strategies over some others. To collect the required data, the student version of questionnaire developed for the purposes of this study was distributed to 100 intermediate high school students who were selected based on their scores on a proficiency test. The matching teacher version of the above-mentioned questionnaire was also distributed to 30 EFL teachers in language institutes. Semi-structured interviews with 8 teachers and 10 students were also carried out to provide more in-depth and qualitative data. Results showed that there are some important differences as well as similarities between teachers' and students' perceptions of written corrective feedback on grammatical errors. In addition, some unexpected differences in EFL teachers' perceptions of written corrective feedback were found. Overall, the present study can have some insightful implications for the field of EFL writing instruction.

Abstract-This study aimed at investigating whether direct focused corrective feedback and direct unfocused corrective feedback caused any differential effects on the accurate use of English articles by EFL learners across two different proficiency levels (low and high). The participants were divided into low and high proficiency levels by administering a TOEFL test. Then, sixty learners in each proficiency level formed two experimental groups and one control group, 20 learners in each group. One experimental group received focused written corrective feedback and the other experimental group received unfocused written corrective feedback. The statistical analysis indicated that focused group did better than both unfocused and control groups in terms of accurate use of English articles in both proficiency levels. Therefore, these results suggested that unfocused corrective feedback is of limited pedagogical value, whereas focused corrective feedback promoted learners' grammatical accuracy in L2 writing more effectively.Index Terms-written corrective feedback, focused feedback, unfocused feedback, English articles, proficiency level, grammatical accuracy

Rater effects in performance testing is an area in which much new research is needed (C. M. Myford, personal communication, 23 February, 2010). While previous studies of bias or interaction effect as a component of rater effect have employed experienced teachers as raters (e.g., Schaefer, 2008), the present study uses many-facet Rasch measurement (MFRM) to investigate differential rater effect or rater severity or leniency among three rater types: self-assessor, peer-assessor, and teacher assessor. Essays written in English by 188 Iranian English majors at two state-run universities in Iran were rated both by the students themselves as self-assessors and peer-assessors and by teachers, using a 6-point analytic rating scale. MFRM revealed differing patterns of severity and leniency among the three assessment types. For example, self-assessors and teacher assessors showed the opposite pattern of severity and leniency as compared with peer-assessors when assessing the highest and lowest ability students. This study has implications for the use of peer and self-rating in L2 writing assessment.