assess by + criterion
Showing the standard used for evaluation
Use by with measures, rules, or criteria.
Applicants are assessed by experience and skills.
Assess by or assess on?
Assess commonly uses by to show method or standard. Assess on is uncommon as a direct verb-preposition pattern, though on may introduce a topic or basis in some contexts.
Quick answer
Which preposition is correct with assess?
Use assess by for criteria, methods, or measurement standards. Assess on is usually not idiomatic as a fixed pattern after the verb. However, on can introduce a topic in longer structures such as assess students on grammar.
Teachers often assess by performance rather than attendance.
The report was assessed by independent experts.
The instructor assessed students on pronunciation and fluency.
The report was assessed by independent experts.
The instructor assessed students on pronunciation and fluency.
Choose the pattern by meaning
These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.
assess on + topic
Testing knowledge of a subject
In educational contexts, on can introduce the topic being tested.
Students were assessed on vocabulary at the end of the course.
assess for + purpose
Evaluating suitability or need
Use for when checking whether someone qualifies for something.
Patients are assessed for mobility issues during admission.
assess against + standard
Comparing with a benchmark
Against is common when evaluation involves official standards or targets.
The project was assessed against safety guidelines.
See the difference in context
The same subject can take different constructions because each sentence answers a different question.
Construction
Example
Meaning
assess by
The essays were assessed by clear criteria.
By introduces the method, judge, or standard.
assess on
The class was assessed on grammar and writing.
On introduces the subject area being tested, mainly in education.
assess for
Doctors assessed him for anxiety.
For shows the condition, purpose, or qualification being checked.
assess against
Performance is assessed against company targets.
Against introduces a benchmark or reference point.
Common mistakes
Some combinations appear in real text but do not mean what learners often assume.
Using on for evaluation criteria
Use by or against for standards and methods.
✕ The applications were assessed on strict criteria. ✓ The applications were assessed by strict criteria.Using by for school subjects
In education, on is more natural for topics being tested.
✕ Students were assessed by mathematics. ✓ Students were assessed on mathematics.Leaving out the object after assess
Assess normally needs an object.
✕ The committee assessed by interviews. ✓ The committee assessed the candidates by interviews.Quick practice
Choose the expression that matches the intended meaning.
1. The candidates were assessed ___ their communication skills.
2. The students were assessed ___ spelling and grammar.
3. The athlete was assessed ___ fitness before the match.
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Frequently asked questions
Is assess on always wrong?
No. It is natural when referring to subjects or topics in tests and education.
Can I say assessed by criteria?
Yes. This means the criteria were used as the basis for evaluation.
What is the most common alternative to assess by?
Assess against is common when comparing results with standards or targets.
Related preposition guides
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