Final answer:
The sentence in question uses correct punctuation, specifically a semicolon, to appropriately join two related independent clauses, making the statement true.
Step-by-step explanation:
The sentence given is 'The participants in the first study were paid; participants in the second study were unpaid.' To determine if this sentence is true (correct) or false (incorrect), one must assess the punctuation and structure. This sentence correctly uses a semicolon to join two independent clauses that are closely related in content. Therefore, the statement is true.