graded on N steps; scored out of N
Suffix attached to a number N, indicating that something is evaluated on an N-level scale or scored out of N points. Common in educational and testing contexts.
This test is graded on a 5-step scale.
Please answer the questionnaire on a scale of 1 to 10.
評価 is the general noun for evaluation or assessment. 段階評価 specifically refers to a graded or multi-level evaluation system.
段階 means stage or level. 段階評価 combines it with 評価 to form a compound meaning evaluation by levels.
Compound of 段階 (stage, level) and 評価 (evaluation). The exact historical derivation is uncertain, but it is a transparent modern compound.