Algebraic
equation solving remains challenging for many secondary school students, with
errors often reflecting underlying conceptual, comprehension, and procedural
difficulties. This study investigated the patterns of errors committed by
Senior Secondary School II (SS II) students when solving algebraic equations in
Kankia Education Zone, Katsina State, Nigeria, using Newman's Error Analysis
(NEA) as the diagnostic framework. A cross-sectional descriptive research
design with a diagnostic assessment approach was adopted. The population
comprised 4,683 SS II students, from which 130 students were selected through
multistage sampling involving simple random selection of two co-educational
public secondary schools and intact class sampling. Data were collected using
the Algebraic Equation Diagnostic Test (AEDT), comprising six structured essay
questions. The instrument was validated by two experts in Mathematics Education
and yielded a test–retest reliability coefficient of .82. Data were analysed
using frequencies, percentages, and a chi-square goodness-of-fit test. Sixteen
specific error types were identified, with errors in tabulating values and
selecting appropriate graph scales being most frequent (8.4% each).
Comprehension errors were the most prevalent Newman category (27.0%), followed
by transformation (26.1%) and process skills (22.8%). The distribution differed
significantly across categories, χ²(4) = 37.83, p < .001. The
findings highlight the need for diagnostic and formative assessment that
prioritises students' comprehension and transformation of algebraic tasks to
inform targeted instruction and remediation