Does base attack in the Bestiary = Attack Bonus?

[Incitatus]

This is pretty basic, but I am just getting into Pathfinder. The Bestiary lists a "Base Atk" value for each monster. Is that value, unmodified, the same as the monster's Attack Bonus? The Core Rulebook says a creature's attack bonus is equal to its Base Attack Bonus + Strength Modifier + Size Modifier, so I would think "Base Atk" in the Bestiary is only the first variable in that equation. But the AC values in the Bestiary already incorporate Dex and Size variables, so I'm not sure why the Base Atk values wouldn't be similarly complete.

Just for example, the Phase Spider's Base Atk is listed as 6, but it is a Large creature with a Strength of 20. Is its Attack Bonus:

6 (Base Atk only)

or

6 (Base Atk) + 5 (Strength bonus) -1 (Size modifier) = 10?

Thanks to anyone who can help a newbie out.

[Are]

The Phase Spider's actual attack bonus is listed under the Melee heading. The Base Atk heading is only the base bonus, with nothing added.

For the Phase Spider, the attack bonus on its bite is +10, which you can see from the line:

Melee bite +10 (2d6+7 plus poison and grab)

[Incitatus]

I see now. Thanks very much!

[DGRM44]

Welcome to Pathfinder, I am still learning myself. Its a fun game system, but it can be a lot to digest and figure out.

[leo1925]

Welcome to pathfinder.
Don't hesitate to ask anything, most of the people in the boards will be happy to help you out.

[Red Wullf]

Are wrote:

The Phase Spider's actual attack bonus is listed under the Melee heading. The Base Atk heading is only the base bonus, with nothing added.

For the Phase Spider, the attack bonus on its bite is +10, which you can see from the line:

Melee bite +10 (2d6+7 plus poison and grab)

Welcome to Pathfinder!

Are is right, of course. The Base Atk is included in the event something enhances the spider, such as a template, spell, etc. Thus, you can modify the attack listed under Melee as the spider's situation changes. The listing under Melee is the total attack modifier for a monster as it appears in the stat block. Changes to the monster will modify this attack bonus, so you'll need to know the base attack to work off of.