Penelitian ini bertujuan untuk menghasilkan sebuah instrumen asesmen diagnostik pada materi bangun datar di kelas IV yang valid berdasarkan validitas, reliabilitas, taraf kesukaran dan daya beda serta mengetahui keefektifan instrumen asesmen diagnostik dari hasil analisis tingkatan kemampuan awal siswa dan angket respon guru. Jenis penelitian yang digunakan adalah Research and Development (R&D) dengan menggunakan model pengembangan ADDIE yang terdiri dari 5 tahapan yaitu: analyze, design, development, implement, evaluate. Soal asesmen diagnostik yang dikembangkan berbentuk pilihan ganda sebanyak 19 butir soal yang sudah memenuhi kriteria dan aspek kevalidan yang dilakukan oleh tim ahli dari aspek materi, konstruksi dan bahasa dengan perolehan presentase 93,5% kategori valid serta analisis validasi tiap butir soal yang ditinjau dari hasil analisis validitas, reliabilitas, tingkat kesukaran dan daya beda. Adapun hasil analisis asesmen diagnostik dapat menunjukkan presentase banyaknya siswa yang teridentifikasi mempunyai kemampuan awal yang sangat baik, baik, cukup, kurang dan sangat kurang. Selain itu, hasil angket respon guru yang bertujuan untuk mengetahui keefektifan produk diperoleh presentase 95% yang termasuk dalam kategori sangat efektif. Dengan demikian instrumen asesmen diagnostik yang dikembangkan valid dan efektif untuk mengidentifikasi kemampuan awal siswa.

Kata Kunci: Instrumen Asesmen Diagnostik, Kemampuan Awal, Model ADDIE, Penelitian dan Pengembangan

The purpose of this study was to create a diagnostic assessment tool for class IV flat shape material that was valid in terms of validity, reliability, difficulty level, and differentiation. It also aimed questionnaires and student initial ability levels. Research and Development (R&D) was the type of research in this study. It employed the ADDIE development model, which had five stages: analyse, Design, Develop, Implement, and Evaluate. The diagnostic assessment questions were developed as multiple choice questions consisted 19 items that met the criteria and aspects of validity, which were carried out by a team of experts from the material, construction, and language aspects, examination of the degree of difficulty, validity, reliability, and distinction with a percentage of 93.5% in the valid category and validation analysis of each item in terms of the results. The percentage of students recognized as having very good, good, fair, bad, and very poor beginning abilities could be seen in the diagnostic evaluation analysis questionnaire. Aside from that, the product’s effectiveness was assessed using a teacher response questionnaire, and the results showed that 95% of the respondents placed the product in the extremely effective category. As a result, the diagnostic evaluation tool created was reliable and efficient in determining the starting abilities of students. Keywords: Diagnostic Assessment Instruments, Initial Abilities, ADDIE Model, Research and Development