What Duolingo score do you need for Northern Michigan University?

The apply page says English test scores are valid for two years, must be valid at the start date of your studies, and must be sent directly from the testing company to Northern Michigan University.

Neither page sets a subscore rule or a separate English level for assistantships.

For comparison, the international FAQ sets IELTS at 6.0 for undergraduates and 6.5 for graduate study.

Neither page describes conditional admission or an English pathway based on a test score. Undergraduates can also meet the requirement with a US high school diploma or an accredited international school diploma.

Requirements vary by programme and change between admissions cycles. The score that binds you is the one on your Northern Michigan programme page and in your offer letter, so check it there before you book a test.