WRITTEN MATHEMATICAL COMMUNICATION SKILLS ON OPEN-ENDED PROBLEMS: IS IT DIFFERENT BASED ON THE LEVEL OF MATHEMATICS ABILITY?

: This study aims to describe students' written mathematical communication skills in open-ended problems based on their mathematical abilities. This research was conducted at grade VII-A of SMPN 1 Pamekasan. This research uses descriptive qualitative research. The instruments used were the Mathematical Ability Test (MAT), Written Mathematical Communication Skills Test (WMCST) on open-ended problems, and Interview Guidelines. The results showed that subjects with high and moderate mathematical ability were able to meet three indicators of written mathematical communication skills, namely being able to express mathematical ideas through writing, demonstrate and convey visually; able to understand, interpret and evaluate mathematical ideas in writing, as well as in other visual forms; and able to use mathematical notations in the structure to write down ideas and relationships with situation models in writing. Meanwhile, subjects with low mathematics ability can fulfill 2 out of 3 indicators of written mathematical communication skills, namely being able to express mathematical ideas through writing, demonstrate and convey visually; unable to understand, interpret and evaluate mathematical ideas in writing or other visual forms; and able to use mathematical notations in the structure to write ideas and relationships with situation models.


INTRODUCTION
n Permendiknas Number 22 of 2006 concerning Standard Content of Mathematics Subjects, one of the objectives to be achieved in mathematics learning is the ability to communicate ideas about mathematical objects being studied by students. In this case, communication skills are very important to raise a problem and solve it. Students need to be trained to have the ability to communicate in mathematics learning. Communication skills become one of the conditions that play an important role as it helps in the process of preparing thought and connecting ideas with other ideas that can fill up the things lacking in the whole network of students' ideas (Syafitri, Saragih, & Astuti, 2018: 587).
Communication is the process of conveying meaning in the form of ideas or information from one person to another through certain media (Hardjana, 2003: 11). Agree with Roger in Majid (2016: 282), which defines communication as a process in which there is an idea that is sent from the source to the recipient to change its behavior so that communication requires more than one person and one of them as a source (sender) and the other as a receiver of information and ideas in the hope of giving new knowledge to the receiver. In mathematics, receiving and conveying information is not easy. This is due to the mathematics with lots of terms and symbols. Therefore, communication in mathematics needs to be owned by every student.

METHODS
This type of research is qualitative with a descriptive approach. As explained by Fraenkel, Wallen, and Hyun (2008: 422), namely; "Research studies that investigate the quality of relationships, activities, situations, or materials are frequently referred to as qualitative research". This research was conducted in the even semester in grade VII of SMPN 1 Pamekasan. The subjects in this study were three students from grade VII of SMPN 1 Pamekasan. The procedures for selecting research subjects were: (1) Determining the research class from grade VII SMPN 1 Pamekasan. In this study, the research class is grade VII-A SMPN 1 Pamekasan which consists of 32 students. The reason the researcher chose this grade VIIA student was based on the information from the mathematics teacher where this class was the most complex and representative of the regular class in choosing subjects with high, medium, and low mathematics abilities compared to the other regular classes. Making it easier for researchers to choose research subjects. (2) Select three research subjects. The researcher chose three subjects from the selected class with low, medium, and high mathematics ability. Therefore, the researcher conducted a mathematics ability test first to find out which students have low, medium, and high ability. Then from each of the results of the mathematics ability test, 3 research subjects were selected with the category of high mathematics ability, namely 80 ≤ mathematical ability ≤ 100, medium mathematics ability, namely 65 ≤ mathematical ability ≤ 80, and low mathematics ability if mathematical ability < 65. (3) Can communicate well. Determining the subject also takes into account the teacher's considerations related to the subject's communication skills to express their opinion or way of thinking orally or in writing. The importance of researchers considering the communication skills of the subject, the goal is that the disclosure of mathematical communication skills with open-ended problems can be done well. (4) Willing to be the subject of research.
For the function of the researcher as the main instrument to run well, it is necessary to have assistive instruments in the form of mathematics ability test, test of mathematical communication skills on open-ended problems, and interview guideline. The mathematics ability test is used to take three research subjects from the high, medium, and low categories. The test is in the form of essay questions and adapted from the National Examination (UN) questions for the last three years. The written mathematical communication skill test (WMCST) on open-ended problems was used to obtain data about the students' written mathematical communication skills in open-ended problems in grade VII SMPN 1 Pamekasan. The form of this test consists of questions that refer to Wijaya's opinion about aspects of mathematical communication skills that will be measured in this study include: (1) the ability to express mathematical ideas through writing, demonstrate and convey them visually; (2) the ability to understand, interpret and evaluate mathematical ideas in writing, as well as in other visual forms; (3) the ability to use mathematical notation in its structure to convey written ideas and relationships with the situation model. The interview guideline was made based on the explanation of each indicator of mathematical communication skills. Interviews were conducted to clarify students' answers to open-ended questions that had been done. Besides, interviews were conducted to reveal further information provided by students. Through interviews, students can be more clearly express their answers so that it will be easier for researchers to analyze the answers they give. The interview method used is a semi-structured method because the questions given during the interview depend on the situation, skills, and answers given. The interview guideline used in this study is as follows. b. Why do you use these mathematical symbols or notations? c. What is the relationship between the symbols or mathematical notation?
Before being used, the mathematical ability test (MAT) instrument, the written mathematical communication skills test (WMCST) instrument on the open-ended problem test, and the interview guideline were validated by two validators with the following conditions: (1) feasible to use if at least two validators said they were feasible to use; (2) feasible to be used with improvement if at least two validators say it is suitable to be used with improvements or one validator says it is suitable for use and one validator says it is suitable to be used with improvements; (3) It is not suitable for use if at least two validators say it is not suitable for use.
In this study, the data analysis techniques used were data reduction, data display, and conclusion drawing. Meanwhile, to check the validity of the data, the researcher used time triangulation technique by comparing and checking the results of the test questions carried out at different times using the same questions or having the same level of difficulty. By giving different tests with an equal difficulty level, consistency, and accuracy of data obtained regarding mathematical communication skills in open-ended problems become valid and reliable. The details of time triangulation technique in this study are explained as follows: (1) Tests and interviews were carried out on tests of written mathematical communication skills on open-ended problems, which are hereinafter referred to as tests and interviews 1. At different times, tests and interviews were carried out on tests. written mathematical communication skills on open-ended problems (equivalent to test questions 1), hereinafter referred to as tests and interviews 2. (2) The results of the test and interview 1 are compared with the results of the second test and interview if the same trend is obtained, data collection on the research subject is complete and conclusions can be drawn. If the same trend is not obtained, tests and interviews are conducted on tests of written mathematical communication skills on open-ended problems (equivalent to test questions 1 and 2), hereinafter referred to as tests and interviews 3. (3) If the results of tests and interviews 3 tend to be the same as the results of tests and interviews 1, then the data on written mathematical communication skills tests on open-ended problems is obtained from the results of tests and interviews 1 and 3. If the results of tests and interviews 3 tend to be the same as the results of tests and interviews 2, then data on written mathematical communication skills tests on open-ended problems were obtained from the results of tests and interviews 2 and 3. (4) If the comparison of all the data still has a different tendency, a written mathematical communication skill test and interview will be carried out on an open-ended problem repeatedly until valid data is obtained. Data or information is said to be valid if there is consistency, the similarity of views, opinions, or thoughts on the results of tests and interviews conducted by researchers.

RESULT AND DISCUSSION
Based on the data recapitulation of student scores in terms of mathematical ability, the research subjects taken were (1) students who have high, medium, and low mathematics scores and mathematics skills tests; (2) can communicate well; (3) willing to be the subject of research. The names of research subjects in this study are as follows: (1) RLH as a subject of high mathematics ability (SHMA), (2) APA as a subject of medium mathematics ability (SMMA), and (3) TPL as a subject of low mathematics ability (SLMA).
Then to find out students 'mathematical communication skills in Openended problems, the researcher conducted two tests using WMCST 1 and WMCST 2. In the following, WMCST 1 and WMCST 2 were presented in this study to determine students' mathematical communication skills in open-ended problems.

Written Mathematical Communication Skills Test 1 (WMCST 1)
Mr. Fikri wants to hold his son's wedding. He plans to make a luxurious stage. Mr. Fikri plans to make a stage in the shape of an upright T. With an upright size of 5m × 5m, while the horizontal size is 15m × 5m. Around the stage, decorations are installed at a cost of Rp 5.000,00 each meter. The entire surface of the stage is covered with carpets with a rental fee of IDR Rp 8.000,00 m 2 each. Determine: a. The area of the stage b. The cost of installing all the decorations; c. All carpet rental costs;

Figure 2. Written Mathematical Communication Skills Test 2 (WMCST 2)
The following will explain the results of the analysis of students' mathematical communication skills in open-ended problems.

High Mathematics Ability Subject
The following is an excerpt from an interview with SHMA on Openended problems at WMCST 1. : To make it easier to find the answer. Researchers: What is the relationship between symbols or mathematical notation? SHMA : To find out the results being asked.
Based on interview quotes and answers to subjects with high mathematics ability, it is revealed that subject can meet all indicators of written mathematical communication skills, namely subject is able to express mathematical ideas through writing, demonstrate and convey visually; the subject is able to understand, interpret and evaluate mathematical ideas in writing, as well as in other visual forms; and the subject is able to use mathematical notation in its structure to write ideas and relationships with situation models. Subject is able to express mathematical ideas through writing by expressing the size of the stage as well as the cost of perimeter decoration and carpet rental costs and demonstrating and conveying visually by drawing a perpendicular stage. Subject is able to understand by finding the area of the stage first, looking for the perimeter by multiplying the cost per meter and per meter rental fee times the stage area, and interpreting by expressing the shape of the stage consisting of 2 rectangular and square shapes, and evaluating mathematical ideas in writing or other visual forms using different methods or solutions. Subject can use mathematical notations of multiplication and addition to more easily find answers in their structure to write ideas and relationships with situation models in writing, namely to find answers.
In general, it can be concluded that the subject with high mathematics ability can meet the three indicators of written mathematical communication skills. This is in line with the results of research by Nastahwid, Irawan, and Susanto (2016: 620) that the students' answers show that students have met the communication standards of NCTM (2020). Like the answers shown by S1 and S2, it can be seen in problem 1 that students have used mathematical language to express mathematical ideas correctly, namely making assumptions from each of the known data in the problem. Likewise in problem 2, students have used the language of mathematics to express mathematical ideas correctly, namely making assumptions from each of the data that has been known in the problem. The first step that S1 and S2 do is express their mathematical ideas, students write down the data known from the questions so that students can determine the solution strategy. Furthermore, after the calculation is done and the correct results are obtained. You can see the communication that arises, they can pour ideas to answer questions. It is because researchers do not insist on using certain methods to solve problems. S1 and S2 are given the freedom to determine the method they use according to the concepts they already have.
Besides, high mathematics ability subjects have the ability to solve problems in more than one way. This is in line with the results of research by Nastahwid, Irawan, and Susanto (2016: 620) that from the students' answers, there are creative ideas that arise so that they can show mathematical communication and are challenged to answer questions without being fixated on just one way and not. stick to one formula only on the basic competencies that are being studied at that time. This is also reinforced by previous research conducted by Zuhrotunnisa (2015: 74) that the subject is able to interpret problems in a complex manner (the subject is able to compare one data with another).

Medium Mathematics Ability Subject
The following is an excerpt from an interview with SMMA on openended problems at WMCST 1. Based on interview quotes and answers to subject with medium mathematics ability, it is revealed that subjects can meet all indicators of written mathematical communication skills, namely: Subject is able to express mathematical ideas through writing, demonstrate and convey visually; the subject is able to understand, interpret and evaluate mathematical ideas in writing, as well as in other visual forms; and the subject is able to use mathematical notations in their structure to write written ideas and relationships with situation models.
The subject is able to express mathematical ideas through writing by expressing the size of the stage as well as the cost of perimeter decoration and carpet rental costs and demonstrating and conveying visually by drawing a perpendicular stage. The subject is able to understand calculating the area of the stage, the cost of installing all the decorations, interpreting it by expressing the form of a stage consisting of 2 rectangular and square shapes, and evaluating mathematical ideas in writing, or other visual forms but unable to use different methods or able to finish in one way only. The subject is able to use mathematical notations of multiplication and addition to more easily find answers in their structure to write ideas and relationships with situation models in writing, namely to find out the results.
In general, it can be concluded that the subject with moderate mathematical ability can meet the three indicators of mathematical communication skills. This is in line with the results of research by Nastahwid, Irawan, and Susanto (2016: 620) that the students' answers show that students have met the communication standards of NCTM (2020). Like the answers shown by S1 and S2, it can be seen in problem 1 that students have used mathematical language to express mathematical ideas correctly, namely making assumptions from each of the known data in the problem. Likewise, in problem 2, students have used mathematical language to express mathematical ideas correctly, namely making assumptions from each data that has been known in the problem. The first step that S1 and S2 take is to express their mathematical ideas, students write down the known data from the questions so that students can determine the solution strategy.
Furthermore, after the calculation is done and the correct results are obtained. It can be seen in the communication that arises. Students can express their opinions to answer questions. It is because researchers do not insist on using certain methods to solve problems. S1 and S2 are given the freedom to determine the method they use according to the concepts they already have.
Besides, the moderate ability subject was only able to solve problems in one way. This is in line with the results of previous research conducted by Romadhon (2016: 169) that the subject is able to communicate the solution but not maximally. This is also reinforced by previous research conducted by Zuhrotunnisa (2015: 74) that the subject is still able to interpret problems simply.

Low Mathematics Ability Subject
The following is an excerpt from an interview with SLMA on open-ended problems at WMCST 1. : Because it is the formula for the area of the stage Researchers: What is the relationship between symbols or mathematical notation? SLMA : To find out the results.
Based on interview quotes and answers to subject with low mathematics ability, it is revealed that subjects can only fulfill two of the three indicators of written mathematical communication skills, namely: Subject is able to express mathematical ideas through writing, demonstrate and convey visually; the subject is not able to understand, interpret and evaluate mathematical ideas in writing or other visual forms; and the subject is able to use mathematical notation in its structure to write written ideas and relationships with situation models.
The student is able to express mathematical ideas through writing by drawing the stage and its size, the price of decoration per meter, and the price of renting a carpet per meter as well as demonstrating and conveying visually by drawing two shapes that are put together into a perpendicular stage, the subject is unable to understand, interpret and evaluate mathematical ideas in writing, as well as in other visual forms because the subject is unable to determine the cost of installing all the decorations and the cost of renting the entire carpet, and the subject is unable to use different methods, the subject is able to use mathematical notations of multiplication and addition to solve problems in its structure to write down ideas and relationships with the situation model in writing, namely to find answers or find out the results.
In general, it can be concluded that the subject with low mathematics ability can meet two of the three indicators of mathematical communication skills. Indicators that cannot be fulfilled are that the subject is unable to understand, interpret, and evaluate mathematical ideas in writing or other visual forms. This means that the subject with low mathematics ability cannot solve problems properly. This is in line with the results of previous research conducted by Romadhon (2016: 170) that the subject has not been able to answer calculation questions with a higher difficulty level, they have not been able to do the maximum and the right results. This is also reinforced by previous research conducted by Zuhrotunnisa (2015: 74) that the subject has not been able to express mathematical ideas in writing. Different subjects in open-ended problems judging from the achievement of indicators of written mathematical communication skills between high-ability, medium-skilled and low-skilled students, it can be seen that there are differences in students' mathematical communication skills. Based on the previous data analysis, the achievement of written mathematical communication skills indicators shows that high mathematics ability students can fulfill all indicators and it can be concluded that high-skilled subject can solve problems in more than one way. Moderate ability student can meet all indicators, and it can be concluded that moderate ability student is only able to solve problems in one way, and low ability student can fulfill two of the three indicators of mathematical communication skills in open-ended problems, namely: the first indicator and the third indicator and it can be concluded that low ability subject cannot solve problems properly. The indicator in question is that the subject is able to express mathematical ideas through writing, demonstrate and convey visually; and the subject is able to use mathematical notation in its structure to write written ideas and relationships with situation models.

CONCLUSION
Based on the results of the data analysis that has been described, it can be concluded that written mathematical communication skills in open-ended problems are as follows: (1) Subject with high mathematics ability can fulfill all three indicators of written mathematical communication skills, namely the subject is able to express mathematical ideas through writing, demonstrating and convey visually; the subject is able to express mathematical ideas through writing, demonstrate and convey visually; and subject is able to use mathematical notations in their structure to write ideas and relationships with situation models. (2) Subject with moderate mathematics ability can meet three indicators of written mathematical communication skills, namely subjects are able to express mathematical ideas through writing, demonstrate and convey visually; the subject is able to express mathematical ideas through writing, demonstrate and convey visually; and the subject is able to use mathematical notation in its structure to write ideas and relationships with situation models.
(3) Subject with low mathematics ability can meet two of three indicators of written mathematical communication skills, namely subject is able to express mathematical ideas through writing, demonstrate and convey visually; the subject is unable to express mathematical ideas through writing, demonstrate and convey visually. (4) Subjects is able to use mathematical notations in their structure to write written ideas and relationships with situation models.
Some suggestions that the researcher can put forward are as follows: (a) Students' mathematics ability do vary so that teachers and prospective teachers pay more attention to the level of students' mathematics ability in learning, especially in training to solve problems and pay more attention to students with low and moderate ability so that their abilities could be better.