Independent variable flaws

Language: English
Subject: Natural science > matter
Age: 11 - 13

Independent variable flaws

What is the IV, DV, CVIV, and constant(s)?

Marie wanted to know how long she could keep her carnival goldfish alive. She won a carnival goldfish, fed it A-grade fish food, and gave it a spacious fish tank. 5 days later, the goldfish was dead. Marie concluded that all carnival goldfish would stay alive for 5 days. Why is this flawed?

What is an Independent Variable?