• Communications for Statistical Applications and Methods
• /
• 제28권3호
• /
• pp.307-314
• /
• 2021

We showed that any missing mechanism is reproduced by EMAR or MNAR with equal fit for observed likelihood if there are non-negative solutions of maximum likelihood equations. This is a generalization of Molenberghs et al. (2008) and Jeon et al. (2019). Nonetheless, as MCAR becomes a nested model of MNAR, a natural question is whether or not MNAR and MCAR are testable by using the well-known three statistics, LR (Likelihood ratio), Wald, and Score test statistics. Through simulation studies, we compared these three statistics. We investigated to what extent the boundary solution affect tesing MCAR against MNAR, which is the only testable pair of missing mechanisms based on observed likelihood. We showed that all three statistics are useful as long as the boundary proximity is far from 1.

• 대한화학회지
• /
• 제60권5호
• /
• pp.327-341
• /
• 2016

This study explores the effective visual resources in the “regularity in chemical reactions” unit of ninth grade science textbooks (2009 revised version). The frequency and role of visual resources were initially examined, and the students’ perceptions of visual resources were investigated. The results of the analysis represented the learning material presentation (68%), motivational categories (14%), guide to inquiry procedures (9%), and inquiry results and summaries (8%). According to the investigation of the students’ perceptions of visual resources, the most effective visual resource for motivation is a photograph depicting physical and chemical changes, such as in bread baking and the most effective for learning material presentations in mass conservation, definite proportion, and stoichiometric concept units were a cartoon, graph, and formula representing stoichiometric phenomena, respectively. The most effective resource for guide to inquiry (experimental) procedures were photographs of both instruments and sequential experiment processes; and in the inquiry results and summary category, incomplete tables and graphs for students to work on themselves. The aims of this research are to increase the usefulness of visual resources in the teaching-learning activity and provide informative supplements for the development and improvement of visual resources, according to the students’ perceptions.

• 한국도서관정보학회지
• /
• 제41권3호
• /
• pp.351-372
• /
• 2010

다양한 영화자료의 적극적인 활용과 공유를 위해서 기존의 주요 분류표인 DDC, KDC, LCC의 분류체계를 알아보고, 영화자료의 특성과 함께 기존의 분류체계의 문제점을 파악하고 개선방안을 제시하기 위하여 연구가 수행되었다. 세 체계를 비교한 결과, DDC와 LCC 분류표의 영화관련 항목은 비교적 상세히 전개되어 있었으나 KDC 5판의 영화 관련 항목 수는 매우 미흡하여 영화자료를 포괄하지 못하는 것으로 나타났다. KDC 5판에서는 영화자료의 분류가 4개 강 하에 22개의 하위 항목으로 이루어져 있었지만 본 개선안에서는 9개의 강 하에 53개의 하위 항목을 세분하여 전개하였다. 특히 개선안에는 영화인물, 영화장르, 영화제, 각국의 영화 항목을 추가하였다.