Multiple Spot/Listen checks with one roll?

[Storyteller01]

IMO, to use additive probability is unrealistic, and it devalues the Move Silently skill as a result.

So try it. Get a group of folks and sneak past them (tell them to be alert). Choose conditions that are close to what your rogue may face (dark corner, trees, etc. Parks are great for this). Progressively increase the number to see if it gets harder (remember, when the military goes on alert, they post more guards). Whether your a master thief or not is irrelevant. The question is, does having greater numbers make it harder to sneak past them.

Grouped together, yes. But then your all sitting ducks for a mass attack. It also limits your range of vision and listening.

Walking a post in two's helps to cut down distractions, but its main purpose is to blanket as large an area as possible.

Vietnam is a good example. What were their standard patrol numbers (real question)? Wasn't it close to 16-20? Granted, greater numbers were needed to carry the weapons, but it also improved the odds of detecting and surviving an ambush.

 

[Saeviomagy]

Finally - in terms of gameplay.

What's the incentive for a rogue to avoid a large group of guards if there is no greater chance of him being detected by them?

 

[Lonely Tylenol]

Look, I'm not really arguing that there isn't something to be said for multiple guards. It's a good idea. What I'm arguing is that trying to represent multiple guards by aggregating probability is a poor way of modeling the situation, for reasons I discuss above. After a small maximum number, the guards are going to be making enough noise breathing or shifting from foot to foot to drown out the thief, assuming he's decently sneaky. There's already a game mechanic dealing with this issue: aid another. I don't see why overcomplicating the issue with spuriously useful mathematical models is a preferred solution.

 

[LostSoul]

A possible rule of thumb (I think it might have even been mentioned in the DMG) is to:

- make a single Spot/Listen roll for the whole group
- using the BEST individual modifier
- adding a +2 bonus every time the group doubles in number, BUT
- capping the result at the max for the best individual

That's very elegant. I have been looking for the answer to this problem and I think I've found it.

I think I might also use this for things like a hail of arrows or spears.

 

[KarinsDad]

A possible rule of thumb (I think it might have even been mentioned in the DMG) is to:

- make a single Spot/Listen roll for the whole group
- using the BEST individual modifier
- adding a +2 bonus every time the group doubles in number, BUT
- capping the result at the max for the best individual

Although this sounds good on the surface, it too has some problems:

1) Only a reasonable number of guards should be used. If you have a dozen guards surrounding a four sided building, only three of the guards (at most if some of them are patrolling and some of them are stationary) should be used.

If the guard with the best individual modifier is around the corner or worse yet, around the back, why should you use his ability?

2) The condition of alert. Many people cannot shut the heck up when in groups. I remember a surprise party for my sister in law and brother in law where 30 of us were waiting in their dark house and even though my sister in law and brother in law were a mere 20 feet away outside approaching the house, about a dozen of these people couldn't shut the heck up for the 30 seconds until they got into the door. Talk about annoying the heck out of me.

So, if you have groups of guards, they should be easier to get past then if you have individuals UNLESS they are under strict alert where talking is totally prohibited.

3) The amount of armor the guards and in and whether they are moving. Medium or heavier armor mixed with movement is not conducive to hearing anything well.

4) Whether the guards have helmets on. Helmets are not conducive to seeing much of anything well.


So, I would change your suggestion here slightly to:

- make a single Spot/Listen roll for a few select individuals out of the whole group (the closest ones not moving or the closest moving ones if the closest non-moving ones are more than twice as far away)

- using the BEST individual modifier out of those few select individuals

- adding a +2 bonus every time the group doubles in number to a maximum of +4, BUT

- capping the result at the max for the best individual out of those few select individuals

- penalizing the result based on sound or other distractions in the area, regardless of whether those distractions are made by the guards or by something else

 

[reanjr]

What's a good way to make several Spot/Listen checks with one die roll?

Say a rogue is trying to sneak past a dozen guards. How can I make Spot/Listen checks for them without rolling two dozen times? Is there a rules-based concept to go with on this?

I've thought about rolling for one guard and then adding +1 for every additional guard who would be making a check. But then you could get a situaion where a bunch of guards with only +2 to their checks get a 28 result.

Quasqueton

Say you've got 20 guards. Most likely one of them will roll a 20. The theory is that one would roll a 1, a second would roll a 2, and so on. So, in that situation, I would give them a "roll" of 20. For lesser amount, lower this value by 1 for every two fewer guards. So 18 guards would roll 2-19. Using the 19 value would give you a result.

12 guards would roll 5-16.

This is how I would do Taking 10 in a group.

[edit Additional guidelines for multiple effects stacking:

Just in case someone likes this method, here are some methods for determining how many successes occur. Note, this is not an exact mathematical method, but it gives usable and reasonable results.

Start at 10. For each individual beyond the first, add 1. Every time, you reach the DC of the action, you have one success and you go back down to 10 and keep counting.

And finally, for large groups making attacks (a volley of arrows, for instance) add +1 to the BAB for each individual beyond the first. So, a unit of 20 archers, each with a BAB of +4 could be treated as a single individual with a BAB of +23/+18/+13/+8/+3. You only have to roll 5 attacks now instead of 20. This is taken from Salt and Sea Dogs.

If you need to extend this (for instance with 100 archers) you can repeat this as if you had a number of individuals with a BAB equal to the average of the multiple attacks. For instance (I would suggest doing it until you have a BAB of +30 or less, to maintain as much accuracy as possible while giving you as little work as possible), the average of the +23/+18/+13/+8/+3 attack routine is +13. If you had 5 combatants (5 attacks) at +13, you would treat it as a single combatant at +17. So your unit of archers attacks at +17/+12/+7/+2. This is most accurate with hig ACs.

 

[reanjr]

Well, it's probably more trouble than it's worth, but you could just use the multiplicative property of probabilities. For example, if a character has a 50% of success on a Spot check (Spot +5, DC 15) and he needed to make 5 spot checks, his chance of succeeding on ALL of them would be:

50% ^ 5, or .5 * .5 * .5 * .5 * .5

The math is pretty easy, but I'd just roll a few times.

That's backwards. Your result gives a ~3% chance to spot the rogue. More guards should give greater chances.

You would instead take 10 on the guards' roll, determine what chances the rogue had of accomplishing this, and then use that method. Unfortunately, this takes away the player's fun because he doesn't get to roll. And if you actually roll the guard's check, then you are not getting anywhere near an accurate probability.

 

[reanjr]

o,o2€
Sue

How do you say that? Euros Two? And if it were higher than a Euro would it work like that? For instance 2,30€ would be Two Euros Thirty?

 

[Li Shenron]

- penalizing the result based on sound or other distractions in the area, regardless of whether those distractions are made by the guards or by something else

That's absolutely fine. I didn't specifically mention circumstance modifiers, but it's true I use them quite freely all the time. [I've never considered penalties for mutual distraction however]

Also, if you have guards divided in groups (such as one group per side of the castle) it definitely makes sense to roll separately for each group.

One last thing about the method I mentioned: I think it works so that having 2 guards instead of 1 gives a benefit better than adding 1 guard to a group which is already large (going from 20 guards to 21 isn't as much as an improvement), and also - because of the cap - after some point it makes no difference at all.

 

[Marimmar]

How do you say that? Euros Two? And if it were higher than a Euro would it work like that? For instance 2,30€ would be Two Euros Thirty?

It would be two Euro-cent and two Euro thirty. (at least in germany)

~Marimmar