Stats question

[Malenfant]

When working out the stats for my revised stellar generation tables, I need to know the probability that a mainworld generated using the CT Book 3 rules has size 1+ AND atm 0 AND hydrographics 0 - but since I'm not a stats wiz I can't get my head around how to figure it out.

Here's how to figure things out:

Size is generated using 2d-2 (with no DMs)
Atm is generated using 2d-7+size (with no DMs)
Hyd is generated using 2d-7+size: DM-4 for all hyd rolls since atm=0. If size=1 then hyd=0.


I'd be ever so grateful if some kind maths genius out there could please please please work this out for me...

 

[robject]

P(S1) = probability of a size-1 world = appx 5%
P(S1-A) = prob of size 1+ world = appx 97%

That's as far as I can go without having to think, so instead I'll write a script and see what comes out.

OK, I ran a million worlds and got:

Without the -DM mod:
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">100: 23327, 2.33 %
200: 6262, 0.62 %
300: 3056, 0.3 %
400: 984, 0.09 %
500: 126, 0.01 %</pre>[/QUOTE]With the -DM mod:
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">100: 23258, 2.32 %
200: 19114, 1.91 %
300: 13266, 1.32 %
400: 6786, 0.67 %
500: 1967, 0.19 %</pre>[/QUOTE]Wasn't the rule supposed to be hyd = 2d-7+atm?

 

[rancke]

Originally posted by Malenfant:
When working out the stats for my revised stellar generation tables, I need to know the probability that a mainworld generated using the CT Book 3 rules has size 1+ AND atm 0 AND hydrographics 0 - but since I'm not a stats wiz I can't get my head around how to figure it out.

Here's how to figure things out:

Size is generated using 2d-2 (with no DMs)
Atm is generated using 2d-7+size (with no DMs)
Hyd is generated using 2d-7+size: DM-4 for all hyd rolls since atm=0. If size=1 then hyd=0.

First you have to roll a 3 on 2D for the size. The probability of doing that is 2/36.

The you have to roll 6 or less on 2D to get atm 0. The probability of that is 15/36.

Then you have to roll 10 or less on 2D, unless you meant that a a size of 1 automatically gives a hyd of 0, in which case you don't have to roll at all. The probability would be 33/36.

The final probability is 2*15*33/36*36*36 = 990/46656 = 0.021 or 2.1%.

If a size 1 world automatically has hyd 0 the probability is 2*15/36*36 = 30/1296 = 0.023 or 2.3%.


Hans

 

[Malenfant]

Thanks guys.

Good thing I specified that I needed the hydrographics calculated with a Size modifier. I forgot that Book 3 had that wacky +atm DM instead (which never appears in any version of the game afterwards, including book 6).

That begs the questions, are all the printed UWPs technically wrong because they calculate the hydrographics using the wrong DMs??

 

[Flynn]

Because of the variations in all the UWP generation methods, aren't all UWPs technically wrong in comparison to one method or another?

So long as they're correct by one, neh?

Enjoy,
Flynn

 

[Malenfant]

Well, how varied are the basic UWP generation methods? AFAIK we have the book 3 basic method (with the +atm mod), the book 6 basic method (with the +size mod)... are the later Traveller versions different?

I gather that the Book 6 method is what is supposed be used though, not the book 3 one.

 

[Flynn]

In these regards, there might not be many differences. However, I expect that GT: First In's method has some significant differences in many regards. Also, T20's method does change some aspects of UWP generation, in a manner similar to JimV's alternate method found in the Galactic 2.4 software. I can't recall TNE's variants, but I believe there are a few differences there, as well.

Someday, I think I'll have to make a list,
Flynn

 

[Malenfant]

Oh yeah, GT:FI is radically different.

But what I'm considering here is that the UWPs that were generated for the initial canonical sector data - especially for the Marches and the Rim - used the Book 3 rules. I know that the CT Rim supplement introduced the concept of atm D, E, and F which were later explained in Book 6, but I don't think it changed any other rules.

If those rules were later superceded by the Book 6 basic rules (which essentially were used by every other version of Traveller since then), then technically the UWPs generated using book 3 will not produce results that are consistent with what anyone else produces, and therein lies the contradiction and inconsistency.

 

[mike wightman]

Here's a basic comparison of basic world generation in the various editions of Traveller.

In CT:
World size = 2d-2
Atmosphere = 2d-7+world size
(if world size=0, then atmosphere=0)
Hydrographics = 2d-7+atmosphere
(if world size is 1 or less, hydrographics =0;
if atmosphere is 1 or less, or A or more, apply a DM of -4)

In MT (and LBB6):
World size = 2d-2
Atmosphere = 2d-7+world size
(if world size=0, then atmosphere=0)
Hydrographics = 2d-7+world size
(if world size is 1 or less, hydrographics =0;
if atmosphere is 1 or less, or A or more, apply a DM of -4)

In TNE:
World size = 2d-2
Atmosphere = 2d-7+world size
(if world size=0, then atmosphere=0)
Hydrographics = 2d-7+world size
(if world size is 1 or less, hydrographics =0;
if atmosphere is 1 or less, or A or more, apply a DM of -4)

In T4:
World size = 2d-2
Atmosphere = 2d-7+world size
(if world size=0, then atmosphere=0)
Hydrographics = 2d-7+atmosphere
(if world size is 1 or less, hydrographics =0;
if atmosphere is 1 or less, or A or more, apply a DM of -4)

In T20:
World size = 2d-2
Atmosphere = 2d-7+world size
(if world size=0, then atmosphere=0)
Hydrographics = 2d-7+atmosphere
(if world size is 1 or less, hydrographics =0;
if atmosphere is 1 or less, or A or more, apply a DM of -4)

So it's an even split. Three versions of Traveller World creation use:
Hydrographics = 2d-7+atmosphere (CT, T4, T20),
and three use
Hydrographics = 2d-7+world size (LBB6, MT, TNE).

I know it doesn't help any

 

[mad13142000]

Here's Galactic 2.4's Homebrew method...

1. World Size. Roll 2d6-2.

2. Atmosphere. Roll 2d6-7+Size.
if size=0, atmos=0.
confine range to 0-F.

3. Hydrographics. Roll 2d6-7+Size.
if atmos is 1 or less, DM -4
if size is 1 or less, hydro=0
if atmosphere is A-C, DM -4
if atmosphere is E, DM -2
confine range to 0-A

4. Indigenous Life. Roll d12-1 twice, take lower of two rolls
if atmos is 1 or less, then life = 0
if atmos is A-C, DM -6
if hydro = 0, DM -4
if life is A-B, 50% chance of DM +2
confine range 0-D
if life is D, conduct eco-collapse:
atmos=C
hydro, DM -4
confine hydro 0+

I've noted elsewhere that Galactic has 3 addon codes (similar to PBG) which are Life, Resources, and Exports

5. Resource Level. Roll 2d6-7+Size
confine range 0-F

6. Population. Roll 2d6-2.
if size is 2 or less, DM -1
if atmosphere is 3 or less, DM -3
if atmosphere is A, DM -2
if atmosphere is B, DM -3
if atmosphere is C, DM -4
if atmosphere if greater than C, DM -2
if atmosphere is 6, DM +3
if atmosphere is 5 or 8, DM +1
if hydro=0 and atmos>3, DM -2
if life is 0, DM -2
if life is 7+, DM +2
if res is 0, DM -3
if res is 1-4, DM -1
if res is 5-8, DM +1
if res is 9-C, DM +2
if res is D+, DM +3
confine range to 0-A

6b. Population Multiplier. Roll d9.
if pop is 0, 5 in 6 chance that popmult = 0

7. Starport. Roll 2d6 (use whichever table suits the locality
but remember that high rolls result in
a lower quality starport).
if pop=0, starport=X
if pop=1, DM +2
if pop=2, DM +1
if pop is 6-9, DM -1
if pop is A, DM -2
confine range to A-X

8. Government. Roll 2d6-7+population.
if pop=0 and popmult=0 then gov=0
confine range to 0-F

9. Law Level. Roll 2d6-7+government.
if gov=0 then law=0
confine range to 0-20

10. Tech Level. Roll d6. Modify as per the standard chart
for starport, size, hydro, and pop. Modify as per
standard chart for atmosphere except for D-E range.
Modify as per law as follows:
if is law B-D, DM -1
if is law F+, DM -2
Modify as per government as follows:
if gov = 1 or 5, DM +1
if gov = 13 or 14, DM -2
if gov = 6 or 15, DM -1
if pop=0 & popmult=0 then tech=0
confine lower bound of range to 0

11. Technical Depopulation.
if hydro is 0 or A and pop is at least 6,
then tech must at least be 4.
if atmos is 4, 7 or 9,
then tech must at least be 5.
if atmos is 3 or less or A-C,
then tech must at least be 7.
if atmos is D or F and hydro is A,
then tech must at least be 7.
if tech is less than minimum requred tech then:
pop=0, popmult=0, gov=0, law=0, tech=0, starport=X

The program further weights the results depending on how settled the subsector in question is. This is determined by the Ref prior to generation (you also determine the density of the subsector).
ie: Unsettled, Backwater, Standard, Mature, or Commercial Hub...

Its a pretty good method. The only thing I wish the program had is an extended stellar system generator, but oh well...

-MADDog

 

[Malenfant]

Argh. So T4 and T20 use the Book 3 system?!

So where DOES the Book 6 system stand? Did Marc ever officially specify which was the correct method? Because right there is a pretty big canon contradiction/ambiguity in the core rules.

It makes more sense to link hydrographics to size instead of atmosphere - otherwise you end up with having more liquid on the surface of worlds just because they have exotic atmospheres, instead of because they're bigger (and therefore accumulated more icy planetesimals and comets when they were accreting).