Testing an Argument...

Well, the book specifies 3 tests to make an argument good which consist of the following:

*The premises are plausible
*The premises are more plausible that the conclusion
*The arguments is valid or strong.

Each of these tets are "independent" which means that they don't all rely on each other. One can be right and the others don't necessarily have to be right as well. So when first examining an argument, it is important to see which on of these questions is the easiest to answer first.

Here is my example...

In order to ride the bus, you have to have a valid pass.
Mark has a valid pass
Mark can ride the bus

Now to answer the questions...

The premises are valid because you can't ride the bus without a pass (unless you want to get arrested) and Mark clearly has a valid pass for the day which means he can ride the bus. The premises are true, which means that they are plausible.
In this case, I think the premises are more plausible than the conclusion. The premises have more credibility than the conclusion, even though the conclusion is credible.
The argument is also strong because both premises are true. The argument is also valid because it is not possible for the premises to be true and the conclusion false.