S2-05 · 基础S2-05 · Foundation

概率分布 · 一整杯怎样分给所有候选Probability Distribution · Split One Whole Across Candidates

non-negative shares + total 1

概率分布是一组候选结果及其概率:每项都不小于 0,全部加起来必须等于 1。它不是三杯各自无限加水,而是把同一整杯在候选之间重分配。A probability distribution pairs candidate outcomes with probabilities. Every share is non-negative and all shares sum to one. It is one fixed cup being reallocated, not three independent supplies.

01 · 只有一整杯01 · Only one whole cup

如果“猫”的可能性多拿一点,另外两个候选能不能都保持原样?If “cat” receives more probability, can both other candidates stay unchanged?

02三杯概率水Three Cups of Probability Water

守恒重分配型Conserved reallocation
三杯总量Total volume
1.000
始终守恒always conserved
最大候选Largest candidate
当前最高杯highest cup now
最近操作Last changed
获得指定份额received requested share

检验方法:记住两只杯子的高度,再把第三杯调高。至少一杯必须下降,总量仍显示 1.000。Verification: note two cup levels, then raise the third. At least one other cup must fall while the total still reads 1.000.

03一份分布的 3 个条件Three Conditions of a Distribution

候选 + 份额Candidates + shares
PART 01

候选集合Candidate set

猫、狗、鸟是这次互斥的所有候选结果。Cat, dog, and bird are all mutually exclusive outcomes here.

PART 02

非负份额Non-negative shares

每只杯子的水位只能在 0 与 1 之间。Every cup level stays between zero and one.

PART 03

总量为 1Total equals one

三杯共同瓜分完整的可能性总量。The three cups divide the whole amount of possibility.

CHECK

此消彼长Trade-off

一杯上升时,其他杯必须让出同样总量。When one rises, the others must give up the same total.

04最小机制:所有候选共同分 1Minimal Mechanism: All Candidates Share One

Σ pi = 1
pcat + pdog + pbird = 1
上方每次滑动后都重算另外两杯,使 pi ≥ 0 且总和精确回到 1。Every slider move recalculates the other two cups so each pi stays non-negative and the total returns exactly to one.
提高一杯Raise one cup指定新的概率份额Set a new share
挤压其余杯Compress the others按原比例让出水量Give up water proportionally
总量守恒Conserve total重新相加仍为 1The sum remains one

05边界实验:检验一组伪概率Boundary Test: Inspect a Fake Distribution

主动制造失败Create a failure

声称 0.7 + 0.6 + 0.4Claim 0.7 + 0.6 + 0.4

三项都在 0 到 1 之间还不够;如果总和不是 1,它就不是完整概率分布。主实验的三杯不会被破坏。Keeping each item between zero and one is not enough. If the sum is not one, it is not a complete distribution. The three main cups remain conserved.

尚未执行。检查非负,也要检查总和。Not run yet. Check non-negativity and the total.
每项小于 1 就是概率分布。Values below one automatically form a distribution. → ✓ 还必须非负且全部加总为 1。They must also be non-negative and sum to one.
提高一个候选不会影响其他候选。Raising one candidate leaves all others unchanged. → ✓ 总量固定,提高一项必挤压其余项。With a fixed total, raising one must compress others.
最高概率就是必然发生。The largest probability is certain to occur. → ✓ 最高只表示在当前候选中占比最大。Largest means only the biggest share among candidates.
06 · 一句话带走06 · One line to keep

概率分布把总量 1 分给所有候选,每项非负;调高任意一杯,就能检验其他杯必然让位而总量仍守恒。A probability distribution assigns a non-negative share of one to every candidate. Raise any cup to verify that the others give way while the total stays conserved.