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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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MARKETING GAMES AND SENSITIVITY ANALYSIS FOR ANY NUMBER OF COMPANIES Amir, Almira; Simanjuntak, Ruth Mayasari; Suzana, Yenny; Lubis, Riri Syafitri; Syarah, Fatmah; Fajriana, Fajriana; Zahedi, Zahedi
BAREKENG: Jurnal Ilmu Matematika dan Terapan Vol 20 No 2 (2026): BAREKENG: Journal of Mathematics and Its Application
Publisher : PATTIMURA UNIVERSITY

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30598/barekengvol20iss2pp0927-0940

In the business world, advertising plays a crucial role in shaping market dynamics. This study analyzes advertising competition among companies by calculating the optimal profits for two to four competitors and postulating a general formula for a larger number of companies. Sensitivity analysis is employed to observe how changes in advertising parameters affect profits. The simulation results indicate that in the case of four companies, the optimal spending (Xopt) ranges from 137246 to 191288, while the optimal profit (Popt) ranges from 38693.1 to 92702. The sensitivity analysis shows that companies with higher advertising effectiveness achieve greater profits, whereas those with lower effectiveness tend to experience reductions in both allocation and profit. With the aid of Maple and Excel, this research extends previous advertising competition models by providing a comprehensive framework for optimizing advertising budgets in oligopolistic markets.

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.

Analisa Manajemen Waktu Pelaksanaan Administrasi Di Dinas Kehutanan Provinsi Sumatera Utara Dengan Metode CPM Elpita Sari Hasibuan; Evi Borliana Siregar; Fikri Husin Batubara; Muhammad Vikry Rezky Rambe; Riri Syafitri Lubis
Jurnal IPTEK Bagi Masyarakat Vol 2 No 2 (2022)
Publisher : Ali Institute of Research and Publication

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55537/jibm.v2i2.233

Kerja praktik (KP) merupakan kegiatan akademik yang berorientasi pada bentuk pembelajaran mahasiswa untuk mengembangkan dan meningkatkan tenaga kerja yang berkualitas. Dengan mengikuti kerja praktik (KP) diharapkan dapat menambah pengetahuan, keterampilan dan pengalaman mahasiswa dalam mempersiapkan diri memasuki dunia kerja yang sebenarnya. permasalahan yang terjadi di bagian administrasi yaitu keterlambatan atas proses administrasinya. Maka daripada praktikan mencoba menggunakan Metode CPM untuk menyelesaikan proses administrasi agar lebih efisien. jalur kritis dapat ditemukan dengan melihat total float menghasilkan jumlah sama dengan 0 yang berupa aktivitas kritis dan ditemukan jalur kritisnya sebagai berikut: “ 1-3-4 ”.

Analisis Diskriminan Penggunaan Media Sosial di Kalangan Mahasiswa UIN Sumatera Utara Fibri Rakhmawati; Rina Filia Sari; Riri Syafitri Lubis; Ruth Mayasari Simanjuntak
Jurnal IPTEK Bagi Masyarakat Vol 4 No 2 (2024)
Publisher : Ali Institute of Research and Publication

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55537/jibm.v4i2.1024

Penelitian ini bertujuan untuk menemukan perbedaan signifikan antara mahasiswa yang menggunakan media sosial secara aktif dan tidak aktif di Fakultas Sains dan Teknologi UIN Sumatera Utara, menentukan variabel pembeda di antara kedua kelompok, membangun model diskriminasi dua faktor, serta menguji akurasi model tersebut. Sampel penelitian terdiri atas 1.800 mahasiswa dari 220 program studi, dengan data yang dikumpulkan melalui kuesioner. Kredibilitas dan validitas kuesioner diuji menggunakan SPSS melalui Uji Wilk's Lambda dan F-test. Analisis diskriminan digunakan untuk mengidentifikasi variabel pembeda, seperti akses, unggah foto, perbarui status, membagikan tautan, dan cerita langsung (live stories), serta menentukan proporsi keanggotaan masing-masing kelompok. Hasil analisis menunjukkan adanya perbedaan signifikan antara perilaku mahasiswa aktif dan tidak aktif dalam menggunakan media sosial, dengan validasi silang menunjukkan akurasi klasifikasi sebesar 77,0%. Temuan ini memberikan kontribusi penting dalam memahami pola penggunaan media sosial di kalangan mahasiswa.

Penerapan Model Arima Pada Nilai Penutupan Indeks Harga Saham Gabungan Untuk Data yang Hilang Zam, Elma Dwi Ariana Aprilia; Nabilla, Widi Ihdina; Pohan, Ahmad Syahrial; Lubis, Riri Syafitri
JISTech (Journal of Islamic Science and Technology) Vol 10, No 2 (2025)
Publisher : UIN Sumatera Utara Medan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30829/jistech.v10i2.28361

Penelitian ini bertujuan untuk menerapkan model Autoregressive Integrated Moving Average (ARIMA) meramalkan nilai penutupan Indeks Harga Saham Gabungan (IHSG) harian periode November 2024 hingga November 2025 yang mengandung missing value. Ditemukan sebanyak 121 data hilang yang menyebabkan ketidakteraturan interval waktu, sehingga dilakukan penanganan missing value menggunakan metode interpolasi linear. Tahapan analisis meliputi eksplorasi data, pengujian kestasioneran menggunakan uji Augmented Dickey-Fuller (ADF), differencing untuk mencapai kestasioneran, identifikasi model menggunakan ACF, PACF, dan Extended Autocorrelation Function (EACF), serta pemilihan model terbaik berdasarkan kriteria Akaike Information Criterion (AIC). Hasil analisis menunjukkan bahwa model ARIMA (0,1,1) merupakan model terbaik dengan nilai AIC terendah dibandingkan model kandidat lainnya. Model ini juga memenuhi asumsi diagnostik residual yang meliputi white noise, normalitas, dan homokedastisitas. Evaluasi akurasi model menunjukkan nilai RMSE sebesar 985,29 dan MAPE sebesar 11,61%, yang mengindikasikan kemampuan peramalan yang cukup baik. Dengan demikian, model ARIMA (0,1,1) dapat digunakan sebagai alat bantu dalam peramalan pergerakan IHSG dan mendukung pengambilan keputusan investasi.

Prediksi Permintaan BBM Fasilitas Pegawai Menggunakan Simulasi Monte Carlo Pada PT. Pelabuhan Indonesia Regional I Dian Darmawan; Nova Audry Utami; Riri Syafitri Lubis
APPA : Jurnal Pengabdian Kepada Masyarakat Vol 3 No 2 (2025): APPA : Jurnal Pengabdian kepada Masyarakat
Publisher : Shofanah Media Berkah

Show Abstract | Download Original | Original Source | Check in Google Scholar

Penelitian ini memprediksi kebutuhan Bahan Bakar Minyak (BBM) untuk karyawan PT Pelabuhan Indonesia Regional I selama tiga bulan ke depan (Desember 2024 – Februari 2025) menggunakan simulasi Monte Carlo. simulasi menunjukkan perkiraan konsumsi Solar sebesar 721,72 liter (Desember), 451,96 liter (Januari), dan 451,96 liter (Februari); serta Pertalite sebesar 442,14 liter (Desember), 425,26 liter (Januari), dan 425,26 liter (Februari). Metode ini diharapkan membantu PT Pelindo Regional I dalam mengoptimalkan pengeluaran BBM dan meningkatkan efisiensi operasional .Data konsumsi BBM (Solar dan Pertalite) September-November 2024 digunakan untuk membangun model prediksi

Optimasi Vehicle Routing Problem pada Distribusi Tabung LPG Menggunakan Metode Ant Colony Optimization Simamora, Devitasari; Lubis, Riri Syafitri; Rahayu, Sri Ulfa
Euler : Jurnal Ilmiah Matematika, Sains dan Teknologi Volume 14 Issue 1 April 2026
Publisher : Universitas Negeri Gorontalo

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37905/euler.v14i1.37481

Inefficient distribution can increase operational costs; therefore, determining optimal routes is essential to support an efficient distribution process. This problem can be formulated as a Vehicle Routing Problem (VRP), which concerns optimizing vehicle routes from a depot to multiple destinations with minimum travel distance. This study aims to optimize the distribution route of LPG cylinders at PT Jaya Sari Artha by considering 12 distribution points. The method used is Ant Colony Optimization (ACO), a heuristic algorithm inspired by the foraging behavior of ants in finding the shortest path. The data used consist of actual travel distances between distribution points obtained from Google Maps. The results show that the implementation of ACO in the VRP model produces a distribution route with a total distance of 117.40 km, shorter than the company’s initial route of 134.50 km. Thus, a distance saving of 17.10 km or 12.72% was achieved. These findings indicate that the ACO method is effective in solving VRP and improving the efficiency of LPG cylinder distribution in a real-world case.

Pengaruh Model Pembelajaran Kooperatif Tipe Think Pair Share Terhadap Kemampuan Berpikir Kreatif Matematis Siswa SMP Muhamar Chaniago, Febri; Syafitri Lubis, Riri; Narpila, Suci Dahlya
Educational Journal Vol. 1 No. 3 (2026): FEBRUARI-APRIL
Publisher : Indo Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.63822/vs25ap22

The research, entitled "The Effect of the Think Pair Share Cooperative Learning Model on Junior High School Students' Mathematical Creative Thinking Skills," is based on the fact that in mathematics learning, teachers often teach students in conventional learning, where learning always focuses on teacher explanations. Consequently, not many teachers are able to help students develop thinking skills in solving mathematical problems. Therefore, teachers need to use good learning methods to help test students' creative thinking skills in mathematics. The research methodology used quantitative research with a posttest control group design approach. The study population was students of Madrasah Tsanawiyah Al Ittihadiyah Medan with a sample size of 22 students in the experimental group and 22 in the control group. The sampling technique used by the researcher was cluster random sampling. The data collection technique was a mathematical creative thinking ability test. Instrument validity testing used each formula assisted by using Microsoft Excel. An Independent Sample t-Test was also used to test the research hypothesis. The results of the study revealed that there was an influence between the cooperative learning model of the think pair share type on the mathematical creative thinking abilities of junior high school students. This can be seen from the results of the Independent sample t-test which showed that the significance value was 0.000 < 0.05 so that H0 was rejected and H1 was accepted. From the research findings above, the think pair share type cooperative learning model can be used as an alternative learning model in the mathematics learning process, especially for material that requires creative thinking skills.

Investment Risk Analysis of Gold, the Indonesia Composite Index (IHSG), and BBCA Stock in Indonesia using the Value At Risk (Var) Method With A Variance–Covariance Approach Tanjung, Aida Febriana; Hasibuan, Hani Maulida; Kurahman, Panca Taufik; Nasution, Fakhrur Rozi; Lubis, Riri Syafitri
JISTech (Journal of Islamic Science and Technology) Vol 11, No 1 (2026)
Publisher : UIN Sumatera Utara Medan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30829/jistech.v11i1.28790

Investments in various financial instruments such as gold, the Indonesia Composite Index (IHSG), and individual stocks carry different levels of risk due to market price fluctuations. These differences require investors to understand potential risks in order to manage their portfolios optimally. Therefore, a quantitative risk measurement method is needed. Value at Risk (VaR) is a method used to estimate the maximum potential loss at a given confidence level and time horizon. This study aims to analyze and measure investment risk in gold, IHSG, and BBCA stock in Indonesia using the Value at Risk (VaR) method with a variance–covariance approach. The data consist of monthly closing prices from April 2024 to March 2025, implying a 1-month VaR horizon with confidence levels of 90%, 95%, and 99%. The results show that the VaR value at the 95% confidence level (1-month horizon) is (4,033.25) for gold, (8,064.47) for IHSG, and (7,931.17) for BBCA stock. At a higher confidence level of 99%, the VaR increases to (5,704.31) for gold, (11,405.74) for IHSG, and (11,217.20) for BBCA stock. These findings indicate that IHSG and BBCA stock have higher potential maximum losses compared to gold, consistent with their higher volatility levels. These results suggest that the variance–covariance VaR method provides measurable quantitative risk estimates across different confidence levels and time horizons, making it useful for investment decision-making and structured portfolio risk management.

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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