• Journal of Educational Research in Mathematics
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• v.9 no.1
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• pp.245-261
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• 1999

Proof is an essential characteristic of mathematics and as such should be a key component in mathematics education. But, teaching proof in school mathematics have been unsuccessful for many students. The traditional approach to proofs stresses formal logic and rigorous proof. Thus, most students have difficulties of the concept of proof and students' experiences with proof do not seem meaningful to them. However, different views of proof were asserted in the reassessment of the foundations of mathematics and the nature of mathematical truth. These different views of justification need to be reflected in demonstrative geometry classes. The purpose of this study is to characterize the types of students' justification in demonstrative geometry classes taught using dynamic software. The types of justification can be organized into three categories : empirical justification, deductive justification, and authoritarian justification. Empirical justification are based on evidence from examples, whereas deductive justification are based logical reasoning. If we assume that a strong understanding of demonstrative geometry is shown when empirical justification and deductive justification coexist and benefit from each other, then students' justification should not only some empirical basis but also use chains of deductive reasoning. Thus, interaction between empirical and deductive justification is important. Dynamic geometry software can be used to design the approach to justification that can be successful in moving students toward meaningful justification of ideas. Interactive geometry software can connect visual and empirical justification to higher levels of geometric justification with logical arguments in formal proof.

• The Mathematical Education
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• v.48 no.2
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• pp.149-167
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• 2009

This study was aimed to examine problem-solving ability of fifth graders on two types of mathematical essay problems, and to analyze the process of mathematical justification in solving the essay problems. For this purpose, a total of 14 mathematical essay problems were developed, in which half of the items were single tasks and the other half were data-provided tasks. Sixteen students with higher academic achievements in mathematics and the Korean language were chosen, and were given to solve the mathematical essay problems individually. They then were asked to justify their solution methods in groups of 4 and to reach a consensus through negotiation among group members. Students were good at understanding the given single tasks but they often revealed lack of logical thinking and representation. They also tended to use everyday language rather than mathematical language in explaining their solution processes. Some students experienced difficulty in understanding the meaning of data in the essay problems. With regard to mathematical justification, students employed more internal justification by experience or mathematical logic than external justification by authority. Given this, this paper includes implications for teachers on how they need to teach mathematics in order to foster students' logical thinking and communication.

• Journal of Industrial Convergence
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• v.20 no.11
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• pp.165-175
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• 2022

The purpose of this study is to understand the effect of membership type for subscription service (individual subscription vs. group subscription) on continuous intention, and to verify the mediating effect of ease of justification and the moderated mediating effect of uncertainty. An experiment was conducted on 78 university students. As a result, consumers who use subscription services in group subscription showed higher intention to continue using the subscription service than consumers who use the subscription service in individual subscription. Also, the ease of justification mediates the effect on the intention to continue using. In addition, uncertainty was found to moderating effect of ease of justification on continuous use intention according to the type of subscription. This study understands the psychological mechanism of consumers according to the type of subscription service subscription and provides useful implications for companies that provide subscription services.

• Education of Primary School Mathematics
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• v.16 no.3
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• pp.267-283
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• 2013

Mathematical justification is the process through which one's claim is validated to be true based on proper and trustworthy data. But it serves as a catalyst to facilitate mathematical discussions and communicative interactions among students in mathematics classrooms. This study is designed to investigate the effects of mathematical justification on students' problem-solving and communicative processes occurred in a mathematics classroom. In order to fulfill the purpose of this study, mathematical problem-solving classes were conducted. Mathematical justification processes and communicative interactions recorded in problem understanding activity, individual student inquiry, small and whole group discussions are analyzed. Based on the analysis outcomes, the students who participated in mathematical justification activities are more likely to find out various problem-solving strategies, to develop efficient communicative skills, and to use effective representations. In addition, mathematical justification can be used as an evaluation method to test a student's mathematical understanding as well as a teaching method to help develop constructive social interactions and positive classroom atmosphere among students. The results of this study would contribute to strengthening a body of research studying the importance of teaching students mathematical justification in mathematics classrooms.

• Education of Primary School Mathematics
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• v.14 no.1
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• pp.13-26
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• 2011

The purpose of this research is to analyze geometrical level and the justification process in the proofs of construction by mathematically gifted elementary students. Justification is one of crucial aspect in geometry learning. However, justification is considered as a difficult domain in geometry due to overemphasizing deductive justification. Therefore, researchers used construction with which the students could reveal their justification processes. We also investigated geometrical thought of the mathematically gifted students based on van Hieles's Theory. We analyzed intellectual of the justification process in geometric construction by the mathematically gifted students. 18 mathematically gifted students showed their justification processes when they were explaining their mathematical reasoning in construction. Also, students used the GSP program in some lessons and at home and tested students' geometric levels using the van Hieles's theory. However, we used pencil and paper worksheets for the analyses. The findings show that the levels of van Hieles's geometric thinking of the most gifted students were on from 2 to 3. In the process of justification, they used cut and paste strategies and also used concrete numbers and recalled the previous learning experience. Most of them did not show original ideas of justification during their proofs. We need to use a more sophisticative tasks and approaches so that we can lead gifted students to produce a more creative thinking.

• Journal of Korean language education
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• v.25 no.1
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• pp.83-113
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• 2014

This study aims to examine the change of strategy use by analyzing the refusal sequence of beginner Japanese Korean learners by time difference of 10 weeks. The results of the study are as follows; First, in the solidarity system of politeness(power-, distance-), learners showed similar ability as native Koreans after 10 weeks. Second, in the deference system(power-, distance+), there was a difference according to the situational burden when using strategies. In the invitational setting, the learners sought justification for their refusal or tried to negotiate by explaining in detail as time passed. However, in the request setting, they showed no will to compromise by refusing directly and leading the listener to give up. Third, similar difference was found in the use of strategies depending on the situational burden in the hierarchical system(power+, distance+). While learners could present their justification for refusal by showing their interest in the invitation as time passed in the invitation setting, they expressed straight refusal and were not willing to negotiate in the request setting.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.52
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• pp.311-322
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• 1999

Major problems involved in an electrical utility expansion planning within a time horizon are how to efficiently deal with objectives considering multiple factors and uncertainty. But justification factors in study these days have considered only quantitative factors except qualitative factors. Therefore, the purpose of this paper is to develop a new model for economic evaluation of nuclear power plants through the scoring model with the quantitative and qualitative factors under uncertainty. The quantitative factors use a levelized generation cost method considering time value of money. Especially, the environmental, risk, and safety factors in this paper have been also explained for the rational economic justification of the qualitative factors under uncertainty. This paper not only proposes a new approach method using the scoring model in evaluating economy of the nuclear power plant in the long term, but also provides the more efficient decision making criterion for nuclear power plants under uncertainty.

• Journal of applied mathematics & informatics
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• v.16 no.1_2
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• pp.125-142
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• 2004

We analyze the convergence properties of Powell's UOBYQA method. A distinguished feature of the method is its use of two trust region radii. We first study the convergence of the method when the objective function is quadratic. We then prove that it is globally convergent for general objective functions when the second trust region radius p converges to zero. This gives a justification for the use of p as a stopping criterion. Finally, we show that a variant of this method is superlinearly convergent when the objective function is strictly convex at the solution.

• Journal of The Korean Association For Science Education
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• v.38 no.2
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• pp.249-257
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• 2018

The purpose of this study was to analyze the knowledge and ability levels of middle school students in four areas: conceptual understanding, argument construction, justification schemes, and use of scientific knowledge in a causal explanation for a genetic phenomenon. A group of 162 middle school students who have taken a class titled Genetics and Evolution participated in the study. Each student answered-and justified the answer to-one question pertaining to genetics. Ability levels were rated from level 0 to level 4, with 4 being the top rating. Students were required to choose one of two competing arguments to explain whether green seed pimps and red seed pimps of the same size and shape were the same species or not. Analyzing conceptual understanding: 47% of the respondents provided the correct answer. Analyzing their abilities for constructing an argument: 75% of the students with the correct answer and 42% of the students with the incorrect answer were evaluated to be at ability level 3 or 4 for argument construction. Analyzing the students' justification schemes: "Scientific idea" and "Analogy" were the most frequently used schemes. Analyzing their use of scientific knowledge: of the students who selected the scientific idea justification scheme, 36% used the correct scientific knowledge, but the remainder used inaccurate or nonspecific scientific knowledge. These findings provide implication for encouraging argumentative writing explaining scientific phenomena regarding epistemic practice.

• Journal of Korean Society of Forest Science
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• v.95 no.5
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• pp.551-555
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• 2006

This research was conducted to estimate the use and preservation values of Jirisan national park, using a dichotomous choice contingent valuation. Jirisan national park was estimated to have the use value of 6,377 won per visitor. In terms of preservation value was estimated 13,030 won per housed per year. The results of this research show that Jirisan national park generated considerable use and preservation values, exceeding far greater than current admission fees. The findings also indicate that the estimated economic value provides enough justification for the national park service to increase admission fees in order to maintain the quality of the natural environment. This result may contribute to guidance on the pricing policy of national park managers and practitioners, although public policy may be made in the political arena.