GCSE Business: In the mark schemes, what is the difference between AO1a, AO1b and AO3a, AO3b? OCR Customer Support 28 November 2019 16:22 Updated AO1a refers to knowledge and AO1b to understanding AO3a refers to analysis and AO3b refers to evaluation. Referring them to a and b comes from the Ofqual guidance on the assessment objectives. Related articles GCSE Chemistry A: What adaptations are in place for Summer 2021? Comments 0 comments Article is closed for comments.