Lost Opportunity

Although both factors are in an argument, there is a difference between Strong and Valid arguments. 

Weak/Valid Argument Example :
Errol got offered a job today at 10-2
Errol had class 10-2
So Errol did not take the job because he had class. -__-

Strong/Valid Argument Example:
Errol didn't take a job today. 
So Errol didn't get paid for that job.
 
There are both examples of valid arguments but they differ in strength. The first one, although it's valid, the argument is bad because Errol could've not taken the job because he overslept or didn't check his schedule properly but it doesn't entirely mean he didn't he take it solely because he had class at the same time. The second example is similar but actually stronger because the conclusion is an actual direct result of the initial premise. there is no way that the conclusion can be true without the premise being plausible.