Development of STEM-nuanced textbook to improve students’ mathematical communication skill

This research is development research that aims to develop and to know the quality of Science, Technology, Engineering, and Mathematics (STEM)-nuanced teaching materials that were meet the suitability of characteristics, validity, readability, and improvement of students’ mathematical communication ability. This research uses the stages of Research & Development, including potential and problems; data collection; product design; product test (readability test); trial test; and final product. The results showed that the teaching material met the suitability of the characteristics. The results of the validity test showed a percentage of 88.54%. The readability test results showed a percentage of 63.65%. Analysis of pretest and posttest showed that teaching materials increased mathematical communication ability with the n-gain score of 0.44 in the medium category. Thus, the development of Science, Technology, Engineering, and Mathematics (STEM) nuanced teaching materials is qualified because suitability in characteristics, valid to use, easily understand, and can increase students’ mathematical communication ability.


Introduction
Education has an important role in equipping youth to compete in the future and be able to face the developments of the 21st century. Education is a foundation that can develop student abilities and prepare students for problem-solving, communication, and decision-making skills. Education is the most important aspect of country development [1]. In reality, Indonesia's position in the education and health sector is in the 100th position [2], which shows a decrease of 20 levels from the previous year. The results of the Program for International Student Assessment (PISA) study in 2018 [3] that the average scores on mathematics and science of Indonesian students are below the international average. Whereas, mathematics is a very important lesson, and useful in life [1].
One of the solutions to develop the education sector is developing teaching materials. Teaching materials are all forms of systematics materials used in the learning process [4,5,6]. Teaching materials are proven to be able to assist teachers in delivering material, as well as being able to improve learning outcomes and student motivation [7].
Teaching materials also can be integrated with the STEM approach. STEM is an acronym for Science, Technology, Engineering, and Mathematics. STEM is based on the achievement of science and mathematics and must be appropriate when combined with technology and engineering [8]. Integrated STEM means to combine two or more aspects of STEM in a single project [9]. The STEM approach has been developed in several countries [10,11] and became a worldwide trend [6,12]. Turkey's Ministry of National Education (MoNE) [8], and the United States NGSS [13] recommend the STEM approach

Potential and Problems
Based on the interviews with a mathematics teacher at school, the mathematics teaching material used was a book entitled "Matematika untuk SMP/MTs kelas VII Semester 2" published by the Ministry of Education and Culture. In the book, there are several examples of questions with STEM nuances, but they are not comprehensive and have not facilitated the improvement of mathematical communication skills. Even though mathematical communication skill is one of the abilities that students must have in learning. It becomes the potential to develop STEM-nuanced teaching materials as one of the learning alternatives to improve students' mathematical communication skills.

Data collection
Data collection started from core competencies, basic competencies, competency achievement indicators, learning objectives, concept maps, the benefits of the material being studied, and problems related to STEM. In this study, Basic Competencies of 3.7, 3.8, 4.7, and 4.8 were selected for the basic design. Furthermore, observations were conducted on several students' books in the Mathematics Department library of UNNES to obtain materials information to be developed.

Product Design
This STEM-nuanced teaching material is designed in A4 size. The basic design of the teaching materials was dominated by Times New Roman font and the size was 12-16 pt. The basic design of STEMnuanced teaching materials consists of 22 pages, consist of the front page, preface, table of contents, core competencies, basic competencies, objectives of teaching materials, concept maps, benefits and linkages with other sciences, learning motivation, learning materials, let's summarize, test competencies, glossary, and references.
The contents of STEM-nuanced teaching material adjusted to the modified format of the student's book analysis from the Ministry of Education and Culture [30], including (1) aspects of the suitability of STEM-nuanced teaching material content with basic competencies; (2) the breadth, depth, current condition, and accuracy of the learning materials on STEM-nuanced teaching materials; (3) shows examples of learning materials (knowledge, factual, conceptual, and procedural) in each chapter of the student book related to STEM; (4) the suitability of learning activities in STEM-nuanced teaching materials: and (5) the assessment in the STEM-nuanced teaching materials.

Characteristics of STEM-nuanced Teaching Materials.
The STEM-nuanced teaching materials met the suitability aspects of the characteristics and can be used in learning based on the validation results of 7 validators. Besides, five validators suggested revision in several contents. The validator's suggestions include adjusting the material with the first core competencies, adding apperception, and updating the material with the current condition. After the revision was made, teaching materials have had the characteristics according to the Ministry of Education and Culture's book analysis format [30].

Validity of STEM-nuanced Teaching
Materials. The validity of teaching materials consists of 3 aspects, namely content, presentation, and language validity. The assessment of the validity of STEMnuanced teaching materials was adopted from the assessment guidelines for mathematics textbooks published by the National Education Standards Agency (BSNP).  Table 1, it was obtained the validity of STEM-nuanced teaching materials had excellent criteria. The content aspect obtained excellent criteria. Teaching materials developed based on science concepts will be worthy [31]. The presentation aspect obtained excellent criteria because equipped with illustrations that support the learning material, so it makes students interested and loves the teaching materials [31]. The language aspect obtained excellent criteria. The use of Language-Enhanced Spelling (EYD) in STEM-nuanced teaching materials make it easy to understand [31]. Thus, the STEM-nuanced teaching materials on direct and inverse proportion was valid and can be used in the learning process.

Product Test (Readability Test)
The readability test was conducted on 26 students of the VII-C class of SMP Negeri 3 Patebon. Readability test obtained an average percentage score of 63.65% with easy to understand criteria. According to [32], the teaching materials has high level readability. It means that the teaching materials has good quality.

Trial Test
STEM-nuanced teaching materials applied in Problem Based Learning (PBL) models. In this study, learning was conducted online using the Google Classroom and WhatsApp in VII-F class of SMP Negeri 3 Patebon.
The prerequisite test was carried out in a normality test at the pretest and posttest. The normality test was carried out using the SPSS 24 application. The hypothesis used was  Table 2 below. Based on Table 2, the n-gain score is 0.44, which indicates the improvement of mathematical communication skills with medium criteria. The improvement not only occurs in the overall average score but also occurred in each indicator of mathematical communication skill. The following picture is the pretest and posttest result of mathematical communication indicators.   Figure 2 below.

Figure 2. The N-Gain Result based on the Indicator of Mathematical Communication Skills
Based on Figure 2, the ability to express mathematical ideas in writing, the ability to use mathematical terms and notations to present ideas, and the ability to evaluate mathematical ideas in writing increased with medium criteria. Meanwhile, the ability to express mathematical ideas in tables/graphs increased with the high criteria.
These results indicate that STEM-nuanced teaching materials on direct and inverse proportion materials have a positive influence on improving mathematical communication skills. This supports the research of [21] that teaching materials with the STEM approach can improve the communication aspect in problem-solving skills.

The Final Product
The final product in this study is a STEM-nuanced teaching material on direct and inverse proportion materials and facilitated by mathematical communication indicators on each problem presented. In the end, the teaching material was registered as copyright at the Directorate General of Intellectual Property.

Conclusion
Based on the results and discussion, STEM-nuanced teaching materials on direct and inverse proportion had fulfilled the characteristic of student book guidelines published by Ministry of Education and Culture in 2018, STEM-nuanced teaching materials was valid and can be used in the learning process, easy to understand, and can improve students' mathematical communication skill. It can be concluded that STEM-nuanced teaching materials was qualified. The recommendation of this study is further research about the development of STEM-nuanced teaching materials that contain other materials or other mathematical skills.