Post/Author/DateTime	Post
SheldonSmith 01-07-05, 01:22 PM	I am DMing a game last night. The party just used a magic key to open a door. The key when it opens the door makes it nearly impossible for the door to be closed again without arcane lock. The key cannot be used to reseal the door. So I figure a Knowledge(arcana) check DC(20) would sufice to tell them that the key could not be used to close/lock the door. All four party members have knowledge(arcana), So I say all of you roll a Knowledge(arcana). You are not going to believe this. The Rogue/Bard rolls a natural 20. The Wizard rolls a natural 20. The Psy Warrior rolls a natural 20. Then for the heck of it the Cleric rolls and guess what... A NATURAL 20!!!!! What are the odds of four players rolling four different dice rolling 4 natural 20s one after the other?????? It was just amazing.
Mr_Smiley 01-07-05, 01:26 PM	What are the odds of four players rolling four different dice rolling 4 natural 20s one after the other?????? Yeah, that is pretty amazing. In case you really are interested in the odds, it is 1 out of 160,000. In other words, don't expect to ever see it happen again :)
Thoronmir 01-07-05, 01:27 PM	Sounds to me like the "secret" of the key was more widely known than you thought. :D
kardock 01-07-05, 01:35 PM	:heehee
Board_Rider 01-07-05, 02:24 PM	Sounds to me like the "secret" of the key was more widely known than you thought. :D Now thats funny!!! Yet so sad at the same time. So much for DM prep......
General_Ridley 01-07-05, 04:57 PM	you should make a door that looks locked. give them what looks like a magical key, and make a DC equal to 21 + the highest Knowledge Arcana skill modifier in the group. Watch them never figure out that all they have to do is push.
ManinDarkness 01-07-05, 05:01 PM	P - I go through the door. DM - The door is closed. P - I unlock the door. DM - The door is unlocked. P - OK, I go through the door. DM - sigh...
Loopy 01-07-05, 06:24 PM	160,000 Wow.
Sinaz 01-07-05, 07:51 PM	Yeah, that is pretty amazing. In case you really are interested in the odds, it is 1 out of 160,000. In other words, don't expect to ever see it happen again :) Never tell me the odds!
Santrilla 01-08-05, 04:01 AM	P - I go through the door. DM - The door is closed. P - I unlock the door. DM - The door is unlocked. P - OK, I go through the door. DM - sigh... Heh. What life would be like if you were DMing in a MUD. P- I go north. DM- You're at the fountain. P- I go north. DM- You're at the marketplace. P- I go west. DM- You're in the bakery. P- I buy 7 loaves. DM- The baker takes 7sp from you. P- I go east. DM- sigh...
jaspercrey 01-08-05, 09:57 AM	Many years ago, as a Hallowe'en special-session, I ran a modern rpg loosely based on John Carpenter's "The Thing" . . . Anyway, by the end of the night the players had cornered the monster in a chamber, doused it with deisel fule and were preparing to set the thing ablaze with signal-flares. Wouldn't you know it, all three players rolled natural 1's for their 'attacks' - resulting in three dud flares!!!! Classic moment for my group.
General Dorsey 01-08-05, 10:36 AM	Oddly enough, the odds are really only 5% since each die is an individual event. If looked at as one event, then: 1/20 * 1/20 * 1/20 * 1/20 = 1/160,000 or 0.00000625%.
SilverFoxKnows 01-08-05, 01:18 PM	and she rolls in the open where everyone can see. She says she visualizes the number she wants. Whatever, it works. One of the players has said repeatedly if he's manning the BBQ and his turn comes up he wants her to roll his attacks. What are the odds? Or did I marry a witch? ;) Frank
clarkvalentine 01-08-05, 02:21 PM	She says she visualizes the number she wants. Whatever, it works. What are you doing here? Take her to Vegas and make a little dough. ;)
Vriishnak 01-08-05, 08:12 PM	Oddly enough, the odds are really only 5% since each die is an individual event. So you're suggesting that it's equally likely to roll 4 (or 30, or 800) 20's in a row as it is to roll the first one? *buzz* Wrong. The odds are 1/160 000.
StevenO 01-08-05, 08:45 PM	It's too bad all the 20's came up for a skill check when only one needed to succede. The story would be far more interesting if they all managed that trick during an opening round of combat, four potential criticals--ow.
General Dorsey 01-09-05, 02:14 AM	So you're suggesting that it's equally likely to roll 4 (or 30, or 800) 20's in a row as it is to roll the first one? *buzz* Wrong. The odds are 1/160 000. Actually, because the events have no influence on each other (they are independent of each other), the odds are 5%. The odds that any of those dice rolls a 20 is 5%, and is unchanged regardless of how many dice are rolled. If, however, the dice have an effect on each other (for example, using open ended rolls), then the odds would be multiplied as I showed in my first post.
clarkvalentine 01-09-05, 11:05 AM	Actually, because the events have no influence on each other (they are independent of each other), the odds are 5%. The odds that any of those dice rolls a 20 is 5%, and is unchanged regardless of how many dice are rolled. Nope, Vriishnak is right. The chance of each independent event is 1 in 20. The chance of all four being 20 is 1 in 160,000. Think of it this way: What are the chances of rolling, say, exactly 55 on percentile dice? It's 1 in 100 - even though the chances of each digit individually coming up 5 are 1 in 10. The chances of you getting "heads" in a coin toss is 50%. Getting heads twice in a row is 25%. Three times is 12.5%. (Don't believe me? Try it!)
General Dorsey 01-09-05, 11:34 AM	At this point I'm going to leave to leave you to your inaccuracies. Having taken Statistics and getting getting a rather decent grade, I'm going to assume that I know what I am talking about. I don't have to try anything, because I understand how statistics work. If you can show me how the first die roll or flip of the coin influences the others, then great, I'll admit I don't know what I am talking about. Since that is unlikely to happen, I'll simply back out of this thread.
StacyCat 01-09-05, 11:44 AM	At this point I'm going to leave to leave you to your inaccuracies. Having taken Statistics and getting getting a rather decent grade, I'm going to assume that I know what I am talking about. I don't have to try anything, because I understand how statistics work. If you can show me how the first die roll or flip of the coin influences the others, then great, I'll admit I don't know what I am talking about. Since that is unlikely to happen, I'll simply back out of this thread. Okay, statistics boy. You are looking at two different items. The first is, yes, the chance of the "next" die roll being a 20 is 5%. 20-20-20-20 has the same chance of coming up as 1-5-13-20. The probability of any sequence of numbers coming up exactly how you write them is the same. Just like flipping a coin. HHHHH has the same chance of coming up as HTHTH. The chance of that exact combination coming up is the same, but it has no affect on the chance of the next roll or flip being different. If he had asked what the odds were of the next player rolling a 20, the answer would have been 5%, or 1 in 20. But, the question was, what are the odds of that paticular combination. That answer is 1 in 160,000. If the players had rolled a 1-13-2-20, that exact combination would have had the odds of 1 in 160,000. We just percieve it as being more "special" or "unusual" because they are the same numbers.
Santrilla 01-09-05, 11:46 AM	A Maths Reject's two copper pieces... Chance of the first dice being 20: 5%. Chance of the second dice being 20: 5%. Chance of the third dice being 20: 5%. Chance of the fourth dice being 20: 5%. Chance of the first AND second AND third AND fourth dice all being 20: 5% x 5% x 5% x 5% = 0.00000625, which is 0.000625%. You're right, each dice is a seperate event. P(dice A is 20), P(dice B is 20), P(dice C is 20), and P(dice D is 20). But the FIFTH event is P(dice A is 20 AND dice B is 20 and... so on).
clarkvalentine 01-09-05, 12:52 PM	At this point I'm going to leave to leave you to your inaccuracies. Having taken Statistics and getting getting a rather decent grade, I'm going to assume that I know what I am talking about. If you want to compare resumes, I've taken several statistics, statistical thermodynamics, and applied mathematics courses, both undergrad and graduate level. What's more, I actually use it on a fairly regular basis in my career, so if we can make assumptions based on that sort fo thing, I'll assume that I'm right. Practical experiment: Roll a single d20. Record how many rolls it takes you to roll a single 20. I'll wait. .... There, took you about a minute, right? Okay. Now, take 4d20. Record how many times it takes you to roll all 20s on 4d20. I'll wait. .... Still rolling? OK, I'll keep waiting... ...... Dude, I have to go to bed soon, you're still rolling? See how that works?
Obiwho? 01-09-05, 01:09 PM	The odds of rolling four 20s in a row is the same as the odds of rolling any other sequence of four numbers (e.g., 4, 13, 7, 19 or 16, 11, 18, 6): 1/160,000. A sequence of four 20s stands out (perceptually), because of the special place of the natural 20 within the rules. Otherwise, it is no more remarkable (statistically) than any other four numbers being rolled in a row.
Mysticaloctopus 01-09-05, 03:10 PM	I once had a plot ruineded by this kind of thing. It was 10th level average, and the group's monk (3 attacks) knocked the villain to 0 hp, with 2 crits from her 3 attacks. The villain was meant to run once he was too weak to win and leave it to his minions, but no, the group went and got all his cool magic items. i mean, It was a plot device but he'd stolen a vorpal longsword from a Wizard's guild armoury where potent items were kept safely... then a fighter got his hands on it... ruined a lot of a story and taught me my lesson... RIG THE DICE! :rofl:
Wayward Son 01-10-05, 11:34 AM	you should make a door that looks locked. give them what looks like a magical key, and make a DC equal to 21 + the highest Knowledge Arcana skill modifier in the group. Watch them never figure out that all they have to do is push. Which leads to one of my favorite traps (courtesy of good ol' Grimtooth, no less). Same set up as Ridley mentioned, the door is unlocked, but the mechanism appears to be locked. If the "lock" is picked or the key used to "unlock" it, the door locks. Madness ensues. :D For extra flavor (or lethality), add a nice pit trap with your favorite bit of nastiness, right under the door latch, which is armed only when the door is "unlocked" and opens when the door handle or latch is pulled/pushed to open the door. :evillaugh
Vriishnak 01-10-05, 01:22 PM	If you can show me how the first die roll or flip of the coin influences the others, then great, I'll admit I don't know what I am talking about. Since that is unlikely to happen, I'll simply back out of this thread. They don't directly influence each other, but in order to get 4 20's in a row, each additional dice roll has the requirement that the previous rolls came up 20. The 4th die had a 1/20 chance of coming up 20, as did each of the previous dice, but in order for all to have been 20's, the previous numbers rolled had to come into effect, making further rolls dependent on the rolls they followed. I don't know if you followed that, and I don't understand why you'd assume that you're the only person on these boards to have taken maths.
Elendur 01-10-05, 01:38 PM	It'd be interesting to try to estimate how often 4 20's are rolled. Most times people report odd dice results, they are talking about one person's rolls in a given session. I think in those cases people usually have selective memories about what was rolled over the whole course of the session. They remember the 20's (or 1's) and forget about the other numbers rolled in between. However in this case 4 dice were rolled at once, so its impossible to misremember the event. (They could just be lying, but I don't see any sense in that). So let's say there are 1000 D&D groups who have at least one member that would report a 4 20's die roll to the boards. If the groups met once a week, and on average once per session had the opportunity to roll 4 20 siders all at once, there would be 52,000 chances to roll 4 20's. That would mean we should see a report like once every 3 years or so.