Hey there folks...

I've read a few posts but haven't quite managed to wrap my brain around 1 idea in particular.

When trying to make something more difficult, does upgrading the challenge dice or adding a setback dice have more of an effect?

Adding a setback does more to reduce the chance of success. Upgrading a difficulty die mostly increases the amount of threat and the chance of Despair.

Increasing the amount of negative dice rolled increases the likelihood of rolling failures and threats. So adding setbacks make checks harder to succeed.

Turning a difficulty (purple) die into a challenge (red) die, know as upgrading, doesn't much alter the likelihood of rolling failures. It does make the check more likely to include an extra threat, but that is rather negligible in my experience. Mostly, the whole point of upgrading checks is to introduce the 1 in 12 possibility that a red die will roll a despair. More red dice means more chances for a despair.

Now, when you upgrade a pool and there are no purple dice left in it to become red, that is when you add a purple. Adding a purple through upgrading does increase the chances to roll failure and threat in a meaningful way.

So any talent, ability, GM fiat, whatever that adds purple dice has huge impacts on the roll's difficulty. Setbacks do this to, but to less of an extent. Upgrading purples to reds, statistically, really doesn't alter how hard a check will be, but it does allow for despair results.

It surprises me that upgrading to challenge die has no effect on success - there's 9 potential failures out of 12 sides, compared to 4 failures out of 8 sides on the difficulty. Granted, this is my English major mathematics working, but isn't that 75% chance vs 50%?

I've found this link most useful in trying to wrap my head around the dice probabilities in this system:

http://maxmahem.net/wp/star-wars-edge-of-the-empire-die-probabilities/

I've found this link most useful in trying to wrap my head around the dice probabilities in this system:

http://maxmahem.net/wp/star-wars-edge-of-the-empire-die-probabilities/

I read that, but it still looks to me from what's written there that challenge dice do increase the odds of failure. Am I reading it wrong?

No, looks like you are spot on. According to this at least.

If you want to make something more difficult (i.e. increase the difficulty), add a Difficulty die.

Hey there folks...

I've read a few posts but haven't quite managed to wrap my brain around 1 idea in particular.

When trying to make something more difficult, does upgrading the challenge dice or adding a setback dice have more of an effect?

But trying to do the math is not helpful, IMO. Best to just stick with the thematic uses of the dice. AoR CRB page 28, "Increase, Upgrade, or Add" sidebar has the info that is most helpful when determining what dice to use.

More dice make it harder.

Always start with an easy check

Next begin adding setback, it rewards the PC's who get setback removal talents. Almost every check should have setback!

Only increase Difficulty if you want the task to be harder and you have already added setback.

Upgrade the check for dangerous, risky or outright crazy checks, or for a Destiny Point flip (but i think thats the weakest way to use a DP IMHO). Basically if there is a chance of something really bad happening, upgrade.

But don't fret the probabilities, if in doubt add more setback after a couple of sessions it gets super easy to eyeball a difficulty for a task.

On a related note never have a single roll require success for the story to advance. If you know your PC's must complete a task then any check to perform that task should only govern time taken and side effects, not weather or not they actually completed the task.

I've found this link most useful in trying to wrap my head around the dice probabilities in this system:

http://maxmahem.net/wp/star-wars-edge-of-the-empire-die-probabilities/

I read that, but it still looks to me from what's written there that challenge dice do increase the odds of failure. Am I reading it wrong?

No, you're correct, they do increase the odds of failure slightly. It would be more obvious if there is only one difficulty die and it's upgraded. But usually you're dealing with a pool of dice, which buffers a single upgrade somewhat. In actual play the effect is minimized, partly because of the interaction between the positive dice is also highly variable. A single upgrade to difficulty means more if you're rolling against one positive die, but less so against 2 or more.

The odds are also obfuscated by the fact that there are two axes, not just one. Really, the important thing about upgrading and adding setback is they increase the range of negative results. If you blank out on your positive dice, the possible results with an upgrade and setback can be a lot worse.

If you have a beginner game or one of the modules (or the adventure at the end of the core book), there are good difficulty examples for new characters. Run through a couple of these and you'll get the hang of it.