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Riri Syafitri Lubis

Universitas Islam Negeri Sumatera Utara, Medan, Indonesia

Author-ID : 3325332

Religion Agriculture, Biological Sciences & Forestry Humanities Biochemistry, Genetics & Molecular Biology Chemical Engineering, Chemistry & Bioengineering Chemistry Civil Engineering, Building, Construction & Architecture Computer Science & IT Control & Systems Engineering Decision Sciences, Operations Research & Management Earth & Planetary Sciences Economics, Econometrics & Finance Education Electrical & Electronics Engineering Energy Engineering Environmental Science Health Professions Industrial & Manufacturing Engineering Languange, Linguistic, Communication & Media Law, Crime, Criminology & Criminal Justice Library & Information Science Materials Science & Nanotechnology Mathematics Mechanical Engineering Medicine & Pharmacology Physics Public Health Social Sciences Transportation Other

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Penerapan Metode Regresi Probit Biner dalam Menganalisis Faktor-Faktor yang Berpengaruh pada Tingkat Partisipasi Angkatan Kerja Wanita Utami, Ristika Dian; Lubis, Riri Syafitri; Cipta, Hendra
Justek : Jurnal Sains dan Teknologi Vol 8, No 2 (2025): Juni
Publisher : Unversitas Muhammadiyah Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31764/justek.v8i2.29162

Abstract: The female labor force participation rate (LFPR) describes the percentage of the female population of working age who are engaged in economic activities. In this condition, the problem that often arises is that the LFPR of women is still lower than the LFPR of men, and the gap between the two is quite far. The purpose of this study is to find out what factors affect the LFPR of women in North Sumatra Province. The method used is binary probit regression method. The data revealed that 45.5% of districts/cities in North Sumatra Province were classified as low LFPR category. The results showed that the level of education (X1) and the informal sector (X5) had a significant effect on female TPAK with a classification accuracy value of 93.9%, indicating that the binary probit regression model used was able to classify the data correctly with a high level of accuracy.Abstrak: Tingkat partisipasi angkatan kerja (TPAK) wanita menggambarkan persentase populasi wanita pada usia kerja yang terlibat dalam kegiatan ekonomi. Dalam kondisi ini, masalah yang sering muncul adalah TPAK wanita masih lebih rendah dari TPAK laki-laki, dan kesenjangan antara keduanya cukup jauh. Tujuan dari penelitian ini yaitu untuk mengetahui faktor-faktor apa saja yang berpengaruh terhadap TPAK wanita di Provinsi Sumatera Utara. Metode yang digunakan adalah metode regresi probit biner. Data mengungkapkan bahwa 45,5% kabupaten/kota di Provinsi Sumatera Utara tergolong dalam kategori TPAK rendah. Hasil penelitian menunjukkan tingkat pendidikan (X1) dan sektor informal (X5) berpengaruh signifikan terhadap TPAK wanita dengan nilai ketepatan klasifikasi sebesar 93,9% menandakan model regresi probit biner yang digunakan mampu mengklasifikasikan data dengan tepat memiliki tingkat akurasi yang tinggi.

Application of k-prototypes algorithm to smoking addiction at FST UINSU medan Ritonga, Nurhalimah; Lubis, Riri Syafitri
Desimal: Jurnal Matematika Vol. 7 No. 3 (2024): Desimal: Jurnal Matematika
Publisher : Universitas Islam Negeri Raden Intan Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24042/djm.v7i3.24374

One of the addictive chemicals that can cause addiction is cigarettes. By combining smoking data among students of the Faculty of Science and Technology (FST) at UINSU Medan, this study seeks to overcome the problem of smoking. The K-Prototypes approach is one of the ones that is applied. Microsoft Excel 2010 and IBM SPSS Statistics are programs used to analyze research data. A sample questionnaire of FST students from UINSU Medan provided data. The findings showed that the K prototype had an impact on smoking factors, study programs, types of cigarettes, the number of cigarettes smoked, and the early age of smoking. There are 19 objects in Cluster 1, 21 objects in Cluster 2, and 25 objects in Cluster 3 students in each cluster. According to the cluster data of the K-Prototypes method, the smoking factor was caused by friends in cluster 1, which included early-age smokers (12.789) with 1.895 packs of salt warehouse cigarettes. In the second group of early smoking age groups (15.810), 1.381 packs of salt warehouse cigarettes were smoked, and the smoking factor was associated with the family. In the third group of early-age smokers (20.44), there were 1.96 packs of Marlboro cigarettes, and friends were a factor in smoking. Thus, the three study programs at FST UINSU Medan require a lot of attention from schools, families, and students.

Optimizing portfolio performance in indonesian banking stocks: An empirical application of the markowitz mean-variance framework Pulungan, Ahmad Fauzan; Riri Syafitri Lubis
Desimal: Jurnal Matematika Vol. 8 No. 2 (2025): Desimal: Jurnal Matematika
Publisher : Universitas Islam Negeri Raden Intan Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24042/nxebn152

This study aims to construct an optimal investment portfolio in Indonesia’s banking sector using the Mean-Variance Markowitz approach. Employing a quantitative descriptive method, the research analyzes monthly closing stock prices of 10 banking companies listed on the Indonesia Stock Exchange from January to December 2024. Data processing was conducted using Microsoft Excel, including return calculation, risk measurement through standard deviation, covariance matrix formation, and portfolio optimization via the Sharpe Ratio. The findings reveal that the optimal portfolio consists of BRIS and PNBN stocks, achieving the highest Sharpe Ratio of 0.6639, which reflects a well-balanced risk-return profile. Conversely, the minimum-risk portfolio yielded a negative return, highlighting that lower risk does not always translate to profit. These results affirm the effectiveness of the Markowitz model in supporting rational investment decision-making, particularly for young investors.

DYNAMICS OF RAINFALL AND TEMPERATURE IN NORTH SUMATRA PROVINCE: COMPREHENSIVE ANALYSIS OF TEMPORAL TRENDS Lubis, Riri Syafitri; Suzana, Yenny; Syarah, Fatmah; Fajriana, Fajriana; Rozi, Fachrur; Nusantara, Badai Charamsar
BAREKENG: Jurnal Ilmu Matematika dan Terapan Vol 19 No 1 (2025): BAREKENG: Journal of Mathematics and Its Application
Publisher : PATTIMURA UNIVERSITY

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30598/barekengvol19iss1pp215-226

This research aims to analyze the temporal trends of rainfall and temperature in North Sumatra Province, focusing on the Medan and Deli Serdang regions. The data used in this study was obtained from the Central Statistics Agency of North Sumatra (BPS Sumut) and spans the period from January 2000 to December 2022. The Mann-Kendall test was applied to identify trends, Sen's Slope Estimator measured the trend slope, and Pearson correlation analysis assessed the relationship between rainfall and temperature. Key findings indicate that Medan has a higher monthly rainfall average than Deli Serdang, with both regions showing a significant increasing trend in rainfall, although the rise is gradual. Additionally, a positive trend in temperature was identified, reflecting broader climate change patterns. However, the correlation between rainfall and temperature was weak, indicating minimal direct interaction between these variables in the study areas. These results contribute valuable insights into climate dynamics and are critical for the development of climate change adaptation strategies in North Sumatra Province.

Optimizing Profit-to-Cost Ratios in Bakery Production Using the Hasan–Acharjee Fractional Programming Method Adisty, Fahliza; Lubis, Riri Syafitri
CAUCHY: Jurnal Matematika Murni dan Aplikasi Vol 10, No 2 (2025): CAUCHY: JURNAL MATEMATIKA MURNI DAN APLIKASI
Publisher : Mathematics Department, Universitas Islam Negeri Maulana Malik Ibrahim Malang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18860/cauchy.v10i2.35738

Production optimization under resource constraints can be effectively modeled using Linear Fractional Programming (LFP), where the objective function is defined as a profit-to-cost ratio. This study applies the Hasan–Acharjee method to optimize production planning in a household-scale bakery enterprise in Indonesia, considering four product types and three resource constraints (materials, labor, and equipment). The model was reformulated as a single linear program and solved using LINGO 21.0. Validation against the classical Charnes–Cooper transformation confirmed identical optimal solutions, demonstrating the robustness of the Hasan–Acharjee approach. Sensitivity and trade-off analyses further revealed how variations in costs and production capacity influence profitability. The results highlight both the theoretical relevance of the Hasan–Acharjee method in fractional programming and its practical applicability to small and medium-sized enterprises seeking efficient resource utilization under limited conditions.

Maksimasi Keuntungan Layanan Jasa Be Clean Laundry Dengan Menerapkan Metode Branch And Bound Syahputra, Bayu Teza; Lubis, Riri Syafitri; Cipta, Hendra
Zeta - Math Journal Vol 6 No 2 (2021): November
Publisher : Universitas Islam Madura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31102/zeta.2021.6.2.1-5

The purpose of this research is to find the maximize benefits from Be Clean Laundry business. In optimize laundry business by looking at the limited resources of the business used branch and bound method. Using the branch and bound method assisted by QM software in more optimal laundry, coat 53 kg, doll 32 kg, blanket 95 kg, bedcover 105 kg, gordyn 91 kg, and clothes 805 kg with a profit of Rp. 4.027.000, while the previous profit based on estimate made by the laundry Owner of Rp. 4.000.000 increase of 0,7 %.

Probabilistic Model of Back Order Policy on Dodol Pulut Raw Material Inventory Control With Linear Programming Br Siahaan, Erika Handayani; Riri Syafitri Lubis
KUBIK Vol 10 No 1 (2025): IN PRESS
Publisher : Jurusan Matematika, Fakultas Sains dan Teknologi, UIN Sunan Gunung Djati Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15575/kubik.v10i1.49121

The high production costs of Dodol Pulut Raya further emphasize the importance of implementing a systematic, measurable, and effective inventory control strategy to maintain profitability, operational efficiency, and long-term business stability. This study applies the Probabilistic Back Order Policy Model combined with the Simplex Linear Programming method to determine the most optimal raw material management policy, taking into account demand uncertainty, supply variability, and the risk of stock shortages that could disrupt production smoothness. This approach comprehensively integrates precise safety stock calculations to minimize stockouts, reduce production delays, and ensure raw material availability so that customer needs can be consistently, timely, and sustainably met. The analysis results show that the implementation of this model can significantly reduce annual production costs from IDR 509,941,040 to IDR 338,719,300, resulting in cost efficiency of IDR 171,221,740 per year. This finding demonstrates the model's effectiveness in minimizing total inventory costs while enhancing competitiveness and operational sustainability. Additionally, this study provides a practical framework for small and medium-sized enterprises facing fluctuating demand, balancing service levels, safety stock, and overall cost optimization.

Optimizing the use of sewing materials to maximize production output Rakhmawati, Fibri; Rifki, Mhd Ikhsan; Husein, Ismail; Cipta, Hendra; Lubis, Riri Syafitri; Sari, Rina Filia
Abdimas Indonesian Journal Vol. 5 No. 2 (2025)
Publisher : Civiliza Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.59525/aij.v5i2.1043

This Community Service Program aims to optimize the use of sewing materials to maximize production output at Rumah Jahit Nila through the application of a linear programming model in the allocation and use of sewing materials in planning and maximizing production output. The implementation methods include mapping processes and data requirements and formulating a linear programming model relevant to the scale of Nila Sewing House MSMEs, as well as training and live demonstrations using QM as software to determine optimization solutions. The evaluation was conducted on 15 participants using a 1–4 Likert scale instrument with four assessment indicators, namely, training content, presenter's subject-matter expertise, event facilities, and benefits of the program. Descriptive analysis showed an overall average of 3.43 on a scale of 4, with a percentage level of 85.8%, which is in the Very Good category. In order, the indicator achievements are Presenter’s Subject-Matter Expertise = 3.53 (88.33%), Benefits of the Program = 3.47 ( 86.67%), Training Content = 3.40 (85.00%), and Event Facilities = 3.33 (83.33%). These results confirm that the competence of the speakers and the relevance of the benefits are the main strengths, while the content and facilities of the activities are areas for priority improvement. This program has successfully improved participants' technical capacity in modeling and implementing linear program-based raw material optimization, while also providing a foundation for operational implementation to reduce waste and increase throughput.

Penerapan Logika Fuzzy Pada Pengendalian Mutu Minyak Kelapa Sawit dengan Metode Statistical Quality Control di PKS Ptpn II Pagar Merbau Auliya Ramadhani, Dhea; Lubis, Riri Syafitri; Widyasari, Rina
Proximal: Jurnal Penelitian Matematika dan Pendidikan Matematika Vol. 8 No. 4 (2025): Volume 8 Nomor 4 Tahun 2025
Publisher : Universitas Cokroaminoto Palopo

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30605/proximal.v8i4.7151

Pengendalian mutu Crude Palm Oil (CPO) merupakan faktor krusial untuk menjaga standar kualitas dan daya saing PKS PTPN II Pagar Merbau. Metode konvensional seperti Statistical Quality Control (SQC) umum digunakan untuk memantau stabilitas proses produksi melalui peta kendali. Namun, SQC memiliki keterbatasan dalam menangani data yang bersifat ambigu atau samar (ketidakpastian) karena pendekatannya yang crisp (tegas), yang hanya mengklasifikasikan status proses sebagai "terkendali" atau "di luar kendali". Penelitian ini bertujuan untuk merancang dan mengimplementasikan sistem pengendalian mutu CPO dengan mengintegrasikan metode SQC dan Logika Fuzzy. Penelitian ini menggunakan data parameter mutu utama CPO, seperti Asam Lemak Bebas (ALB), Kadar Air , dan Kadar Kotoran yang dianalisis terlebih dahulu menggunakan peta kendali SQC untuk menentukan batas-batas kontrol statistik. Selanjutnya, data tersebut dijadikan variabel input untuk Sistem Inferensi Fuzzy (FIS). Logika Fuzzy digunakan untuk memetakan data input yang ambigu ke dalam himpunan fuzzy (misalnya: Rendah, Normal, Tinggi) dan memprosesnya melalui basis aturan (IF-THEN) untuk menghasilkan output kualitatif berupa status mutu CPO (misalnya: Sangat Baik, Baik, Cukup, Buruk). Hasil penelitian menunjukkan bahwa penerapan Logika Fuzzy mampu memberikan penilaian status mutu yang lebih fleksibel, adaptif, dan informatif dibandingkan metode SQC murni. Sistem ini dapat memberikan peringatan dini yang lebih sensitif terhadap pergeseran kecil dalam proses, sehingga membantu manajemen PKS PTPN II Pagar Merbau dalam mengambil keputusan korektif yang lebih cepat dan tepat untuk menjaga konsistensi mutu CPO.

BLACK TEA GRADE CLASSIFICATION USING PROBABILISTIC NEURAL NETWORK (PNN) Sari, Evi Indah; Prasetya, Nurul Huda; Lubis, Riri Syafitri
Journal of Mathematics and Scientific Computing With Applications Vol. 2 No. 1 (2021)
Publisher : Pena Cendekia Insani

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.53806/jmscowa.v2i1.42

North Sumatera tea is known as black tea, one which is produced by PT Perkebunan Nusantara IV Unit Bah Butong which produce 16 types of black tea. This research aims to classify black tea grades using Probabilistic Neural Network method and determine the accuracy value of black tea classification using Probabilistic Neural Network method. Data used are data of characteristics of 16 black tea types with the attributes id, types of tea, colour density, particel weight, particel size and particel shape. To get the best accuracy result, training data and testing data are divided using K-Means Clustering. Futhermore, classificy the testing data using Probabilistik the result obtained a grade 1 classification class totaling 7 records with a brownish black appearance and granutes particel, grade 2 totalling 7 record with a beownish appearance and grade 3 totaling 2 records with reddish appearance and not determine its shape and obtain an accuracy value of 80,00%.

Co-Authors Adisty, Fahliza Ahmad Sugarda Ainun Palihah Almira Amir Ananda, Lyra Anggi Pranata Annisa, Nur Alvi Aprilia, Rima Arjuna, Dimas Bagus Aslam, Fazri Aulia Turrizqiya Auliya Ramadhani, Dhea Batu, Annisa Rajaq Lumban Bella Syahrani Nasution Blaster, Irena Br Siahaan, Erika Handayani Cynthia, Mayang Modelina Dara Nurul Hasnah dewi, mutia hatina Dian Darmawan Didik Santoso Didik Santoso Dinda Renata Cecilia Dwi Haprida Ningsih Elma Dwi Ariana Aprilia Zam Elpita Sari Hasibuan Evi Borliana Siregar Fachrur Rozi Fadhliyah, Annisa Fadilatus Sahraini Siregar Fadillah, Yanna Rezki Fajriana, Fajriana Farwansyah, Mhd Rio Fatmawati, Ayu Isnaini Fernando, Anjas Fikri Husin Batubara Fuja Nauli Pasaribu Giawa, Freddy Gishela Agra Moukia Gurusinga, Ditha Aulia Harleni, Harleni Harleni, Silvia Hasibuan, Hani Maulida Hazizah, Salsabillah Hendra Cipta Heni Pujiastuti Ilham Salim Siregar Ilham Syaputra Indah Kholila Indah, Windi Rezeki Ir Zulkarnain, Ayu Najmita Binti Irena Blaster Ismail Husein, Ismail Kartika , Dinda Khairun Nikmah Kurahman, Panca Taufik Latersia, Egya Dora Lisa Setia Ningsih M Agung Pradana Manurung, Silvi Khairiyah Maudya Nur Azura Mhd Ikhsan Rifki Mohammad Badri Muhamar Chaniago, Febri Muhammad Arfie Munawar Muhammad Farhan Mingka Muhammad Vikry Rezky Rambe Muliawan, Hari Nabilla, Widi Ihdina Nadhila, Nurul Nasution, Alfina Febriani Nasution, Dafa Al Qifti Nasution, Fakhrur Rozi Nasution, Hamidah . Neliwati Neliwati Nenna Irsa Syahputri Nina Amanda Nova Audry Utami Nurmadani Nurmawati Nurmawati Nurmawati Nurul Nadhila Nusantara, Badai Charamsar Oktaviana Oktaviana Palihah, Ainun Pertiwi, Fina Nur Pohan, Ahmad Syahrial Pohan, Siti Rolizah Pradana, M Agung Prasetya, Nurul Huda Pratiwi, Miftah Pulungan, Ahmad Fauzan Putri Harahap, Rahmelia Rahayu, Sri Ulfa Rahmat Darmawan, Rahmat Rakhmawati, Fibri Riani Dwi Lestari Ricka Afriani Rima Aprilia Rima Aprilia Rina Filia Sari Rina Filia Sari, Rina Filia Rina Sari Filia Rina Widyasari Ritonga, Nurhalimah Rivani Kabrina Br Surbakti Rizkina, Ayu Rizky Mulyani Ropiqoh, Ropiqoh Ropiqoh, Ropiqoh Rusydi Ananda Ruth Mayasari Simanjuntak Sahraini Siregar, Fadilatus Sajaratud Dur Samsudin, Samsudin Sari, Evi Indah Serdano, Akbar Simamora, Devitasari Sintia Agustina Siregar Siregar, Evi Borliana Siregar, Fadilatus Sahraini Siregar, Tanti Jumaisyaroh Siti Jubaidah Siti Zunaida Nasution Suci Dahlya Narpila, Suci Dahlya Suci Permata Sari Suendri, Suendri Sulaiman Ananda Harahap Supiah Supiah Susanti, Komaria Susilowati, Rahmi Suzana, Yenny Syafitri, Ellysa Syahfitri, Fatharani Syahputra, Bayu Teza Syahputri, Linna Syahputri, Nenna Irsa Syarah, Fatmah Tanjung, Aida Febriana Tanti Jumaisyaroh Siregar Tri Amisri, Nurul Hasanah Tri Handayani Tri Lutfiah Wardah Turrizqiya, Aulia Utami, Destia Nada Utami, Ristika Dian Vani Hajari Wenny Marta Dolok Saribu Widyasari, Rina Widyasari, Rina Windi Rezeki Indah Wulandari Wulandari Wulandari, Mitha Yahfizham Yahfizham Yoffa Sunita Yulanda Novita Zebua Yulinda, Jeni Zahedi . Zakaria Alfikri Sirait Zam, Elma Dwi Ariana Aprilia

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