Final answer:
The meaning of independent random variables in this context is that knowing how much one machine fills does not help us predict how much the other fills.
Step-by-step explanation:
The meaning of independent random variables in this context is that knowing how much one machine fills does not help us predict how much the other fills. In other words, the amount of ice filled by machine a does not depend on the amount of ice filled by machine b. The two ice machines are independent of each other, meaning they operate separately and their actions do not affect each other.