Many teachers in Indonesia teach students horizontal number lines rather than vertical number lines. However, there are students who use vertical number lines to solve contextual problems that have never been taught in schools. Therefore, this study aims to find out why students use vertical number lines to solve contextual problems. This research is a qualitative research where data is collected by tests and interviews. The results showed that students used vertical number lines based on the context of the given questions.

The purpose of this research was to examine undergraduates' understanding of the central tendency measure from a decision-making perspective. The research adopted a qualitative method by employing an interview and test to obtain the data.  It enrolled 93 undergraduate students who had previously studied basic statistics and applied statistics. Four students were selected for interviews out of the 93 participants. The analysis model used included data condensation, data visualization, and conclusion and verification. A large number of students were unable to provide explanations for their decisions. The majority of students related the test with the necessity of calculating an average or selecting a more straightforward measure. None of the students was aware of the presence and effect of outliers in the data. The undergraduate students demonstrated a lack of awareness of the factors that could influence their decision-making. The students did not consider other variables. The majority of them were unaware of the benefits and drawbacks of using mean, median, and mode to describe data.

The measure of spread is one of the concepts in Statistics that students find complicated. We have to use a specific formula or concept for a specific situation or contextual problem. As a result, people or students sometimes made mistakes or errors in solving statistics problems. Therefore, research to investigate errors made in solving problems involving a measure of spread is necessary. This study aims to describe students' errors in solving problems related to the measure of dispersion. Researchers used a qualitative descriptive approach. We administered the test during the even semester from January to June in the year 2021. The participants were 80 undergraduate students who have completed or taken statistics courses. This test consists of 2 questions that are related to each other. Researchers used the three main steps to analyze the data which consist of data condensation, data display, and verifying and drawing the conclusion. We obtained the data related to students' errors from their test results. The results showed that more than 50% of students still make mistakes on every problem. The mistakes made by participants consisted of the use of formulas, miscalculations, the use of known data, the use of concepts, not giving conclusions, and inconsistencies.

Identitas matematis merupakan salah satu aspek yang penting untuk dimiliki mahasiswa, baik itu mahasiswa di jurusan matematika maupun yang non-matematika. Penelitian ini merupakan penelitian kualitatif yang bertujuan untuk mendeskripsikan identitas matematis yang dimiliki mahasiswa akuntansi. 59 mahasiswa terlibat sebagai partisipan dalam survei yang dilakukan untuk kategorisasi identitas matematis. Peneliti kemudian melakukan wawancara dengan dosen terkait 1 mahasiswa dengan identitas matematis positif dan 1 mahasiswa dengan identitas matematis negatif. Teknik analisis data yang digunakan menggunakan tiga tahapan utama yaitu kondensasi data, tampilan data, dan pengambilan kesimpulan. Hasil penelitian kami menunjukkan bahwa mahasiswa dengan identitas matematis positif dan negatif memiliki perbedaan yang cukup signifikan. Perbedaan tersebut mulai pengetahuan, kemampuan, serta minat dan motivasi. Mahasiswa dengan identitas matematis positif memiliki prestasi matematika yang lebih tinggi dibandingkan mahasiswa dengan identitas negatif. Hal ini ditandai dengan frekuensi menjawab pertanyaan atau soal, nilai, dan tingkat kesulitan soal yang dapat dijawab. Selain itu, mahasiswa dengan identitas matematis positif lebih antusias dan termotivasi dalam mengikuti pembelajaran matematika dibandingkan mahasiswa dengan identitas matematis negatif yang sekadar hanya ingin menggugurkan kewajiban untuk mengikuti perkuliahan. Mahasiswa dengan identitas matematis positif cenderung lebih berinisatif dan mandiri.