Development of Open-Ended Based Mathematics Problem to Measure High-Level Thinking Ability

The study aims to produce Open-Ended based mathematics problems that can be used to measure the high-level thinking abilities of seventh-grade junior high schools' students. The study is developmental research using Plomp model, consisting of the preliminary stage, the prototyping stage, and the assessment phase. The subject was seventh-grade students of junior high school. The teaching material used was about numbers learned at seventh-grade junior high school. Based on the results of the development, it was obtained 15 open-ended based problems in which 12 of them possibly have various answers, and 3 have various possibilities ways of answering. The problems developed are valid with the criteria of the developed problem based on content, the problems have diverse answers or various ways to answer, problems can measure high-level thinking skills; analyzing, evaluating, and creating, and the content of the material is fit to the material about numbers. The problems use clear construct images, clear instructions for working on, adapted Standard Indonesian Spelling System or EYD language, and appropriate sentences to seventh-grade knowledge level, disuse of misinterpreted expressions as well. Related to practicality, it is obtained that students and teachers can use the problem and do it well. The teacher can use it to evaluate students' high-order thinking skills.