Strong vs. Valid Arguments

According to Epstein, a strong argument must have  a way for the premises to be true and the conclusion to be false at the same time.  In order for an argument to be valid, the premises cannot be true and the conclusion must be false at the same time. An example of a strong argument is " Everyday my friends and I noticed that the parking lot is full by twelve. Therefore the parking lot is  full by twelve." This is a strong argument because the premises are true and the conclusion could be false. The premises could be true because it shows proof that my friends and I see the parking lot.  A valid argument would be "The parking lot gets full at 12. Therefore the parking lot is always full by twelve." This is valid because we don't know if the premise is true and the conclusion could be false. We don't know if the premises are true because we don't know who saw the parking lot. It could be some random person who hasn't seen the parking lot.