S2-04 · 基础 · 点名概念S2-04 · Foundation · Requested concept

概率预测 · 不只报答案,还报可能性Probabilistic Prediction · Possibilities, Not Just an Answer

input position → red / blue probabilities → thresholded label

概率预测不是只给一个答案,而是给各候选结果可能性的分配。硬标签只显示哪一边超过门槛;概率还保留“有多接近翻转”的信息。A probabilistic prediction assigns a possibility to each candidate instead of returning only one answer. A hard label reveals which side cleared the threshold; probabilities preserve how close the decision is to flipping.

01 · 标签没变,不代表判断没变01 · Same label, different confidence

“红色 51%”和“红色 99%”都报红色,但它们真的是同一种判断吗?“Red 51%” and “red 99%” produce the same label. Are they really the same prediction?

02拖样本穿过 50% 门槛Drag the Example Across 50%

连续概率 + 离散翻转Continuous odds + discrete flip
红色概率Red probability
p(red)
蓝色概率Blue probability
p(blue)
预测标签Predicted label
严格超过 50%strictly above 50%

操作校验:依次点 49%、50%、51% 三个位置。先看两根柱连续变化,再看标签只在越过门槛后改变。Verification: select the 49%, 50%, and 51% presets. First watch both bars move continuously, then confirm the label changes only after the threshold is crossed.

03一次概率预测的 4 个零件Four Parts of a Probabilistic Prediction

保留不确定性Keep uncertainty
PART 01

输入样本Input example

底部圆点的位置代表这次输入的特征值。The bottom dot's position represents this example's feature value.

PART 02

候选结果Candidate outcomes

本页只有红色与蓝色两个互斥候选。This page has two mutually exclusive candidates: red and blue.

PART 03

概率分配Probability assignment

两根柱同时表达系统对两个候选的相对判断。The two bars jointly express the system's assessment of both candidates.

PART 04

决策门槛Decision threshold

超过 50% 才把连续概率压成一个硬标签。Crossing 50% compresses continuous probabilities into one hard label.

04最小机制:先分配概率,再取较大者Minimal Mechanism: Assign Probabilities, Then Choose

p(red) + p(blue) = 1
ŷ = arg max {p(red|x), p(blue|x)}
上方拖拽改变 x,两项概率连续改变且总和恒为 1。只有最大项从一边换到另一边,ŷ 才翻转。Dragging changes x. Both probabilities move continuously and still sum to 1. ŷ flips only when the larger term changes sides.
移动样本Move example输入特征连续变化Input changes continuously
重算两类概率Recompute both odds一升一降,总和为 1One rises, one falls; sum = 1
越过 50%Cross 50%最大候选改变,标签翻转The winner changes; label flips

05边界实验:在 50% 平局时强报一个答案Boundary Test: Force an Answer at a 50% Tie

主动制造失败Create a failure

抹掉不确定性Erase the uncertainty

把样本放在精确 50% 位置,却强制显示“蓝色”。这会把完全平局伪装成确定答案。Place the example at an exact 50% tie, then force “blue.” This disguises a perfect tie as a certain answer.

尚未执行。正常状态下,50% 会明确显示“平局”。Not run yet. The normal state explicitly reports a tie at 50%.
标签相同,模型判断就完全相同。Matching labels mean identical model judgments. → ✓ 51% 与 99% 可给同一标签,却保留不同不确定性。51% and 99% can share a label while carrying different uncertainty.
概率最高就代表事实一定如此。The highest probability makes an outcome certain. → ✓ 它只是在候选中占比最高,不是事实保证。It is only the largest candidate share, not a guarantee of fact.
概率柱是模型真实置信度。These bars are real model confidence. → ✓ 本页数值只用于教学;真实概率还需校准与验证。These are teaching values; real probabilities require calibration and validation.
06 · 一句话带走06 · One line to keep

概率预测为各候选分配可能性,而硬标签只取概率较大的那一类;拖样本穿过 50%,就能检验概率先连续变化、标签后离散翻转。A probabilistic prediction assigns possibilities across candidates; a hard label keeps only the largest. Drag across 50% to verify that probabilities move continuously before the label flips discretely.