Interval Estimation in Truncated Spline Regression: Analyzing the 2023 Indonesian Democracy Index

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Published: Dec 17, 2025
Keywords:
Democracy Interval estimation IDI Nonparametric regression Truncated spline

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Andrea Tri Rian Dani
Department of Mathematics, Faculty of Mathematics and Natural Sciences, Mulawarman University, Samarinda 75119, Indonesia, Doctoral Study Program of Mathematics and Natural Sciences, Faculty of Science and Technology, Airlangga University, Surabaya 60115, Indonesia
Fachrian Bimantoro Putra
BNI Staff Banking, Future Relationship Manager, Jakarta 10220, Indonesia
Meirinda Fauziyah
Department of Mathematics, Faculty of Mathematics and Natural Sciences, Mulawarman University, Samarinda 75119, Indonesia
Ratna Kusuma
Department of Biology, Faculty of Mathematics and Natural Sciences, Mulawarman University, Samarinda 75119, Indonesia
Darnah
Department of Mathematics, Faculty of Mathematics and Natural Sciences, Mulawarman University, Samarinda 75119, Indonesia
Hadi Koirudin
Department of Mathematics, Faculty of Mathematics and Natural Sciences, Mulawarman University, Samarinda 75119, Indonesia
Chiko Zet Oroh
Department of Mathematics, Faculty of Mathematics and Natural Sciences, Mulawarman University, Samarinda 75119, Indonesia
Raditya Arya Kosasih
Department of Mathematics, Faculty of Mathematics and Natural Sciences, Mulawarman University, Samarinda 75119, Indonesia

Abstract

The truncated spline is a piecewise polynomial that maintains continuity across segments and offers a high degree of flexibility in estimating data that varies significantly across different intervals. This study applies the truncated spline method with interval estimation to analyze the 2023 Indonesian Democracy Index (IDI) data. The objective is to identify the key factors that significantly influence IDI and to evaluate the estimated results of the nonparametric spline regression curve for the 2023 IDI data. The analysis findings indicate that the predictor variables used in this study have a substantial impact on IDI, with a determined coefficient of approximately 97.81%. Based on the interval estimation analysis of the regression curve, it was found that out of 34 provinces in Indonesia, 8 provinces were estimated accurately. These provinces include Kepulauan Riau, DKI Jakarta, Bali, Central Kalimantan, North Sulawesi, Central Sulawesi, North Maluku, and Papua. Additionally, the analysis indicates that 16 provinces have experienced a decline in their Democracy Index (IDI) criteria, suggesting a possible transition in their democratic performance. This situation calls for further in-depth studies to improve their democratic achievement levels. On the other hand, 18 provinces are projected to experience an increase in their IDI performance.

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How to Cite
Andrea Tri Rian Dani, Fachrian Bimantoro Putra, Meirinda Fauziyah, Ratna Kusuma, Darnah, Hadi Koirudin, Chiko Zet Oroh, & Raditya Arya Kosasih. (2025). Interval Estimation in Truncated Spline Regression: Analyzing the 2023 Indonesian Democracy Index. Science & Technology Asia, 30(4), 112–125. retrieved from https://ph02.tci-thaijo.org/index.php/SciTechAsia/article/view/258508
Issue
Vol.30 No.4 (October-December 2025)
Section
Physical sciences
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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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