Rule 8. When in the same sentence two adjectives in different degrees of comparison are used, both should be complete in themselves.
Incorrect- She is as good if not worse than her sister.
Correct – She is as good as if not worse than her sister.
Rule 9. To show whether the difference between the compared thing/person is small or big, we use quantifiers for the comparative degree of an adjective such as (A bit, a little, a lot, far, much, a great deal, significantly, etc). Example:
My hostel is only marginally bigger than yours.
She is a little more popular than her sister in their school.