Final answer:
The statement is grammatically incorrect because the adjectives do not agree with the gender of the noun.
Step-by-step explanation:
The statement Cette petite fille est grand et gros is grammatically INCORRECT.
The adjective grand is masculine and the adjective gros is feminine. Since the noun fille is feminine, the adjectives should match its gender. The correct sentence would be Cette petite fille est grande et grosse.
Learn more about Grammatical correctness in French adjectives