Validity of E-Book Based on Problem-Based Learning with Higher Order Thinking Skills Oriented for Senior High School

Human resources with a high level of thinking abilities, such as critical thinking, creativity, communication, teamwork, independence, cross-cultural understanding, and ICT literacy, are needed for the growth of the 21st century. However, cultivating a high level of thinking abilities is still insufficient and does not fulfill the necessities of the 21st century. An e-book based on problem-based learning and oriented toward higher-order thinking skills is developed as a result of this research. Measurement of the e-book’s validity is the aim of this study. This research used a descriptive methodology and a questionnaire for collecting data. The questionnaire instrument is a validation sheet with four e-book validation criteria consisting of several indicators. E-book validation has shown valid findings with an average of 0.87 valid categories. The results of the research show that the product can be used as a learning resource for students and teachers to achieve learning goals and meet the demands of the 21st century.


Introduction
In the 21 st century, science and technology develop without limits, this is marked by the availability of various online learning spaces such as e-learning, mobile learning, and virtual reality.Humans require a wide range of skills to be able to thrive in the 21st century [1].Humans are also faced with the globalization era which requires high-thinking skills.The ideal conditions call for human resources with high-quality skills and a high level of thinking abilities, including critical thinking, creative thinking, communication, teamwork, independence, cross-cultural understanding, and computation/ICT literacy [2].The 21 st -century learning paradigm emphasizes free, independent, collaborative learning through the use of digital teaching resources, information technology, and electronic communication tools [3].Additionally, physics instruction must be able to promote the development of generic competencies including teamwork, creativity, communication, character development, literacy, and critical thinking [4].Education prepares pupils with moral character and superior cognitive abilities to raise the standard of human resources [5].The field of education demands changes in teaching materials, learning media, facilities, and learning models provided to students [6].A teaching model's roles include creating the curriculum, creating classroom environments, supervising the teaching, and creating the teaching materials [7].To build 21st-century skills and learning paradigms, technology should be introduced into the classroom as a teaching tool.
In reality, learning in schools has not been as expected.It's reflected by the results of TIMSS (Trend in International Mathematics and Science Study) which measures the level of students' critical thinking ability where Indonesia ranks 50th [8].The low quality of education can be seen from several indicators including academic quality through the PISA program [9].In terms of science proficiency, Indonesia is classified in the bottom 9 or ranked 71 st according to the OECD's PISA (Progress for International Student Assessment) report [10].There is still a low level of critical thinking ability and science literacy among Indonesian students in the face of 21 st -century skills.
The government's efforts in Indonesian education are by improving the educational curriculum.Curriculum 13 has been implemented so far, which is student-centered and requires students to have problem-solving skills, critical thinking skills, collaboration skills, and creativity.However, in its implementation, it has not been able to create the expected learning.The covid-19 epidemic has had a significant impact on how people learn.There are currently active learning processes both offline and online.One solution that can be done is to turn learning facilities, such as those that usually use printed materials, into digital teaching materials.The current situation is in line with the demands of skills and paradigms of learning with technology in the 21 st century [2], [3].Teachers and students are challenged to be literate in the sophistication of technology, information, and communication.
Various attempts to meet the demands of the 21st century have been made, but they have not lived up to expectations.Based on field conditions from the results of observations of some schools in the city of Padang.Observations were carried out with physics teacher interviews and the distribution of student questionnaires in each school.According to the interview of the Physics teacher using the teacher interview sheet.The interview results show that the students' HOTS ability is still very low, and only a few students in the class have HOTS ability.Textbooks used in schools are still dominated by textbooks published by publishers (printed teaching materials).Other teaching materials used are videos from YouTube and materials from the internet.Students more often use Whatsapp Group, and Google Forms for learning media during the Covid-19 pandemic.Teaching resources that can support online learning is required since learning models cannot be employed effectively throughout the online learning process.The results of observations made by distributing questionnaires to students found that 72% of students were interested in higher-order thinking skills (HOTS) and agreed that HOTS questions could train high-level thinking skills.
Existing solutions have been carried out in several previous studies, including research: interactive mobile learning media to improve students' HOTS abilities supported with problem-based learning (PBL) models [11], e-module development in Physics lessons based on problem-based learning [12], and development of problem-PBL physics textbooks on elasticity and Hooke's law [13].The presence of independent variables, specifically the orientation of HOTS and variations in the instructional materials generated, distinguishes this study from previous research.Research on the development of Android-based e-books with HOTS questions to help analyze quantities in straight-motion material [14].This research differs from subsequent research in that it makes use of learning models.In terms of the variables used and the development model, it is apparent that the pertinent research conducted by earlier researchers differs from the research that would be conducted.The need for teaching materials and learning models that support the 21 st century is one of them by developing PBL-based ebooks oriented to HOTS.
Efforts to improve learning outcomes by the 21 st -century paradigm need to be carried out by developing teaching materials in the form of electronic books (e-books) based on the PBL model oriented toward HOTS.Advancement of the 21 st century, which uses ICT technology throughout industries, including education, there is a very high chance to adopt learning via mobile devices [15].Human resources with knowledge of networks, the Internet of Things, and cyber-physical systems should be produced through education [16].The e-book displays information that can contain text, images, audio, and video [17].It has a coherent presentation format, both in language, high level of knowledge, and breadth of discussion.The advantages of e-books include the ease of browsing and reading them, saving paper materials, and can be combined with interactive media such as animations, videos, and images.It is hoped this can trigger interest and motivation and thinking about students' addiction in the learning process.In learning physics, media is needed to optimize the learning process and students' interests, and students can actively involve in the learning process with the help of interactive teaching resources [18].Using e-books in the learning process is to meet the characteristics of 21 st -century learning and solve learning problems during the pandemic.The implementation of a learning process that supports students to improve their high-level thinking skills requires an appropriate learning model such as PBL.
The PBL model is a learning process that involves learning characteristics beginning with giving problems that have context with the actual world, and in groups, creating issues and identifying gaps in their knowledge, researching and searching for information related to problems and answers to these problems.It aims to provide real problems to students, group study, find relevant information, collect information, process data, and solve problems given so that students are trained with the 21stcentury paradigm [19].HOTS implementation to fulfill the necessities of the 21 st century.The Partnership for 21st-century Abilities states that students need to be able to build competitive abilities that are centered on the development of higher-order thinking skills [20].Students are taught through HOTS learning how to link ideas, process and apply knowledge, connect information, solve complicated issues, and think critically [21].Based on the demands and problems in the field, the solution offered to comply with the requirements of education and the 21 st -century paradigm is to develop a physics e-book based on the PBL model-oriented HOTS for a valid senior high school.

Method
This study uses the Plomp development model which is limited to the validation stage by experts who are analyzed using descriptive methods.The model is divided into three stages, 1) preliminary research; 2) the development or prototyping phase; and 3) the assessment phase [16].According to the model in the first phase, needs analysis and literature study were carried out.It compiles instruments in needs analysis and makes observations to get preliminary information about learning physics class X. Make observations to see environmental problems and boundaries that will be the content of the ebook.The target achieved gets an overview of various objects in the environment that will be the content of the e-book.
The prototyping stage was carried out after the preliminary research.The prototyping phase makes validation and practicality instruments, multiplying validation and practicality instruments.Conducting self-evaluation is a stage where researchers evaluate and revise the Physics e-book product that has been designed.This evaluation aims to re-examine the e-book so that no errors are found in the e-book that has been developed before being submitted and validated by experts The self-evaluation results were examined before being edited and turned into an e-book.This result is called prototype I. Conducting an expert review, carried out after the self-evaluation stage.At this point, the results that have been evaluated are given to experts for validation.The data collection instrument used in this study was a questionnaire in the form of a validation sheet.The validation sheet was filled in by three experts who contained 4 components, namely material substance, learning design, display (audio-visual communication), and utilization aspects.Validation sheet indicators can be seen in Table 1.It that has been validated by the expert is then revised by the researcher according to the advice of the expert who acts as a validator until the e-book is valid.A valid e-book is called Prototype II.The validation results are processed with Aiken's V formula [22].

Result
Validation results can determine the feasibility of the product and guidelines for revising the product that has been made.There are four assessment components in the validation assessment instrument.First, in the aspects of the material's substance using six indicators.The chart's horizontal axis contains all six indicators.The six indicators include 1) The truth of concepts, principles, and applications, 2) Completeness of the contents of PBL-based e-books oriented HOTS, 3) PBL-based e-book teaching materials oriented HOTS are presented according to the development of science, 4) Problem-based learning-based e-book teaching materials are oriented towards higher order thinking skills which are presented using standard and understandable grammar, 5) The material provided according to the PBL syntax can solve problems, and 6) The material provided contains HOTS (analyzing, evaluating, and creating).The findings of the plot of the value of indicators for the material's substance aspect are shown in Figure 1.

Figure 1. Graph of the Material's Substance's Aspects' Validation Results
Figure 1 describes the values on each indicator of the material substance aspect ranging from 0.78 to 0.89.Of the six indicators, 0.78 with the lowest value, and 0.89 with the highest value.The average validation result of the aspects of the material's substance was 0.83.The material's substance aspect falls within a valid category.
Second, in learning design aspects using ten indicators.The chart's horizontal axis contains all ten indicators.Among the ten indicators include 1) The suitability of the title on the PBL-based physics ebook-oriented HOTS with the material, 2) The suitability of basic competencies (KD) in the PBLbased physics e-book-oriented HOTS, 3) The suitability of HOTS-oriented PBL objectives with KD, 4) The suitability of the material presented in the PBL-based physics e-book oriented HOTS with learning objectives, 5) Conformity of example questions and solutions in the e-book physics PBLoriented HOTS with achievement indicators, 6) The suitability of the exercise in the PBL-based ebook is oriented to higher-order thinking skills with achievement indicators, 7) There is a constituent identity in the e-book Physics PBL-oriented HOTS, 8) There are references in the e-book based on PBL oriented to HOTS, 9) The suitability of PBL syntax in the e-book based on PBL oriented to higher-order thinking skills, and 10) Conformity of practice questions refers to HOTS.The findings of the plot of the value of indicators for learning design aspects are shown in Figure 2. Figure 2 describes the values on each indicator of the learning design aspects ranging from 0.67 to 0.89.Of the ten indicators, 0.67 with the lowest value, and 0.89 with the highest value.The average validation result of the learning design aspect is 0.80.The learning design aspect falls within a valid category.
Third, in the display aspect (audio-visual communication) using five indicators.The chart's horizontal axis contains all five indicators.These indicators include 1) Ease of navigation access between slides on the e-book, 2) Proportionality between the size of the letter and the page space, 3) Media (Images, video, audio) according to the material presented, 4) Conformity of color harmonization and the degree of contrast in the e-book, and 5) The layout and layout are proportional and attractive.The results of each indicator on the display aspect (audio-visual communication) are seen in Figure 3. Fourth, in the utilization aspect using three indicators.The chart's horizontal axis contains all three indicators.Among the ten indicators include 1) The interactivity of the system to users in the PBLbased physics e-book-oriented HOTS, 2) The use of software to support the creation of e-books based on PBL is oriented HOTS, and 3) Retrieval of PBL-based e-book media sources oriented to HOTS.The findings of the plot of the value of indicators for the utilization aspect are shown in Figure 4.

Figure 4. Graph of Utilization Aspect Validation Results
Figure 4 describes the values on each indicator from the utilization aspect ranging from 0.78 to 1.0.Of the three indicators, 0.78 with the lowest value, and 1.0 with the highest value.The average validation result of the utilization aspect was 0.93.The utilization aspect falls within a valid category.Experts gave recommendations for further revision of the results of the validation of PBL-based ebooks oriented HOTS.The advice provided in the form of practice questions is made varied in the C4-C6 range to draw the HOTS indicator.The questions in the exercise should be consistently equipped with known, asked, and answered information that is then added to conclusions, sample questions must also make reference to the HOTS indicator.

Discussion
The material's substance aspect consists of six indicators.Based on the six indicators of material substance, there are the lowest and highest values in these aspects.Indicators of the truth of concepts, principles, and applications; PBL-based e-book teaching materials oriented HOTS are presented according to the development of science; and the material provided contains HOTS (analyzing, evaluating, and creating) got the lowest score of all indicators in the material's substance aspect, which was 0.78.This is because the material indicators provided containing HOTS (analyzing, evaluating, and creating) have not been presented in the correct grouping.HOTS are in the cognitive dimension of analyzing, evaluating, and creating [23].Aspects of the substance of the material one of which includes the correctness of concepts, principles, and applications; and teaching materials are presented D1 D2 D3 Indicator 1,00 1,00 0,78 0,0 Utilization Aspects according to the development of science contained in the creation of instructional materials based on ICT [24].The highest value in the substance aspect of the material is found in the indicator of completeness of the content of the PBL-based learning-oriented HOTS; PBL-based e-book teaching materials oriented HOTS presented using standard and understandable grammar, and the material provided according to the PBL syntax can solve the problem by 0.89.The e-book made is complete which is one of the indicators of the substance of the material contained in the creation of instructional materials based on ICT [24].ICT is used in schools as a teaching tool and as part of efforts to improve education standards in Indonesia [25].The indicator of the e-book's content's completeness receives the highest score.The teaching materials made already use standard and understandable grammar to get the highest score.The creation of instructional materials must take writing indicators into consideration, EYD-compliant writing is one of the requirements for media language eligibility, and utilizing standard language to make the material of the material understandable to pupils [26], [27].The highest value is also obtained in the indicators of the material given according to the PBL syntax that can solve the problem.Real-life and complex problems in the PBL model are used to motivate students to identify and research the concepts, and principles needed to know and solve problems [28], [29].Problem-based learning models can develop higher-order thinking skills, foster independence, and make students confident in solving a problem [30].
The learning design aspect consists of ten indicators.These indicators are 1) The suitability of the title on the PBL-based physics e-book-oriented HOTS with the material, 2) The suitability of basic competencies (KD) in the PBL-based physics e-book-oriented HOTS, 3) The suitability of HOTSoriented PBL objectives with KD, 4) The suitability of the material presented in the PBL-based physics e-book oriented HOTS with learning objectives, 5) Conformity of example questions and solutions in the e-book Physics PBL oriented HOTS with achievement indicators, 6) The suitability of the exercise in the PBL-based e-book is oriented to higher-order thinking skills with achievement indicators, 7) There is a constituent identity in the e-book Physics PBL-oriented HOTS, 8) There are references in the e-book based on PBL oriented to HOTS, 9) The suitability of PBL syntax in the ebook based on PBL oriented to higher-order thinking skills, and 10) Conformity of practice questions refers to HOTS.Based on ten indicators in the learning design aspect, the lowest and highest scores were obtained.The lowest score compared to others is found in the indicator of the suitability of learning objectives with KD, and the suitability of sample questions and solutions in the e-book with achievement indicators with a value of 0.67.This is because it has not met the KD and indicators.This is following the Ministry of National Education's (2010) assertion that one aspect of the creation of teaching materials is the appropriateness of learning objectives with KI-KD and the suitability of exercises with indicators [24].
The highest score in the learning design aspect with a value of 0.89 is found in the indicator of the suitability of the title on the PBL-based physics e-book oriented HOTS with the material; there is a constituent identity in the e-book Physics PBL-oriented HOTS, and there is a reference where it must be found in the aspects of learning design [24].The materials compiled are by basic competencies, indicators, competency standards, and material titles [31].The highest score was also obtained in the PBL syntax conformity indicator in the problem-based physics e-book oriented higher order thinking skills.This is due to the PBL syntax used in the creation of the instructional materials.The syntax of the PBL model is 1) The orientation of participants to the problem, 2) Organizing learners to learn, 3) Guiding investigation, 4) Developing and presenting the work, and 5) Analyzing and evaluating the problem-solving process [32].The advantages of the PBL model generate learners' interest in learning and make students more independent and responsible for their studies by igniting their curiosity [33].
The display aspect (audio-visual communication) consists of five indicators.These indicators are 1) Ease of navigation access between slides on the e-book, 2) Proportionality between the size of the letter and the page space, 3) Media (Images, video, audio) according to the material presented, 4) Conformity of color harmonization and level of contrast in the e-book, and 5) Layout and layout are proportional and attractive.Based on the five indicators in the display aspect (audio-visual communication) the lowest and highest values are obtained.The lowest value compared to others is found in the indicators of Conformity of color harmonization and level of contrast in the e-book with a value of 0.78.This is because there is still a lack of harmonization of colors and the level of contrast which must include the development of ICT-based teaching materials [24].The highest value in the display aspect (audio-visual communication) of 1.0 is found in the indicator of Ease of navigation access between slides on the e-book, and Media (Images, videos, audio) according to the material presented.This is because the navigation between slides on the teaching materials can be accessed easily and the media in the teaching materials are by the material studied [24].
The utilization aspect consists of three indicators.These indicators are 1) Interactivity of the system to users in the PBL physics e-book-oriented HOTS, 2) The use of software to support the creation of e-books based on PBL is oriented to HOTS, and 3) Retrieval of PBL-based e-book media sources oriented to HOTS.Based on the three indicators in the utilization aspect, the lowest and highest values were obtained.The lowest value compared to others is found in the indicator of the collection of media sources.This is due to the lack of learning media sources with a value of 0.78.The highest value is found in the indicator of system interactivity to users on e-books and the use of supporting software for making e-books with a value of 1.0.Teaching materials are made and developed as interactively as possible so that the learning process is not in one direction anymore [15].
Due to the product being developed complies with and incorporates each indicator included on the validation sheet, each aspect's validity value falls under the category of being valid.Students' comprehension of the content can be facilitated by teaching materials constructed with high-quality materials [27].Students will be more interested in teaching materials with interactive audio-visual presentations set up by the syntax of the learning model [34], [35].The novelty and originality of this development research is digital teaching material in the form of an e-book designed with a PBL oriented to HOTS for senior high school.Due to its adaptation to the needs of 21 st -century education and the technologically savvy students' learning methods, an e-book can satisfy the demands of teachers.This research has the drawback of concentrating its efforts on only one model for each topic.Effectiveness and product dissemination are hoped outcomes of the next study.

Conclusion
The results of this validation can be concluded that the average value of problem-based physics e-book validation-oriented HOTS from the four aspects of an assessment is 0.87.Thus, the category of this ebook's average validation value can be deemed valid.An e-book based on PBL oriented toward HOTS can be used in the learning process.According to the study's findings, the product can be used by both teachers and students as a learning resource to reach 21st-century learning objectives.

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The suitability of the title on the PBL-based physics e-book oriented HOTS with the material B1 8 The suitability of basic competencies (KD) in the PBL-based physics e-book-oriented HOTS B2 9 The suitability of the learning objectives of the problem-based physics-based learningoriented HOTS with KD B3 10 The suitability of the material presented in the PBL-based physics e-book oriented HOTS with learning objectives B4 11 Conformity of example questions and solutions in the e-book physics PBL-oriented HOTS with achievement indicators B5 12 The suitability of the exercise in the PBL-based e-book is oriented to higher-order thinking skills with achievement indicators B6 13 There is a constituent identity in the e-book Physics PBL-oriented HOTS B7 14 There are references in the e-book based on PBL oriented to HOTS B8 15 The suitability of PBL syntax in the e-book based on PBL oriented to higher-order thinking skills B9 16 Conformity of practice questions refers to HOTS B10 C. Display Aspects (Audio-visual Communication) C 17 Ease of navigation access between slides on the e-book C1 18 Proportionality between the size of the letter and the page space C2 19 Media (Images, video, audio) according to the material presented C3 20 Conformity of color harmonization and the degree of contrast in the e-book C4 21 The layout and layout are proportional and attractive C5 D. Utilization Aspects D 22 The interactivity of the system with users in the PBL-based physics e-book-oriented HOTS D1 23 The use of software to support the creation of e-books based on PBL is oriented to HOTS D2 24 Retrieval of PBL-based e-book media sources oriented to HOTS D3

Figures 2 .
Figures 2. Graph of Learning Design Aspects Validation Results

Figure 3 .Figure 3
Figure 3. Graph of the Display Aspect Validation Results (Audio Visual Communication)

Table 1 .
Indicator Validation Sheet