In identifying mathematical comprehension skills with a four-tier diagnostic test method can be done by four stages namely: 1) question, 2) level of trust in the answer, 3) reason, and 4) level of trust in the reason.

This research uses descriptive qualitative method with case study strategy. The subject of this study was a grade 1X student at SMP Negeri 4 Purworejo. This study aims to identify mathematical comprehension skills with a four-tier diagnostic test method.

It is influenced by various factors such as intelligence, emotional condition, environment, etc. In understanding the mathematical concepts each student has different abilities.