Probability Explained

Probability Explained
Probability Explained | Ideasthesia

Probability is the mathematics of what we don't know.

Not ignorance—structured uncertainty. The kind of not-knowing that still follows rules. The kind that lets you reason rigorously about dice, diseases, decisions, and data.

This series covers probability from foundations to the theorems that make statistics possible. We'll explore the rules for combining uncertain events, Bayes' theorem for updating beliefs, random variables and distributions, and the remarkable theorems—the Law of Large Numbers and Central Limit Theorem—that explain why statistics works.

What You'll Learn

Foundations: What probability actually means, the axioms that make it rigorous, and the basic rules for computing with uncertainty.

Conditional Probability and Bayes: How new information changes probabilities, and the theorem that underlies modern machine learning, medical testing, and rational belief updating.

Random Variables: The bridge from events to numbers—how to describe uncertain quantities mathematically.

Distributions: The patterns uncertainty takes—binomial, normal, exponential—and when each appears.

Limit Theorems: The deep results that explain why sampling works, why averages converge, and why the bell curve appears everywhere.

Why Probability Matters

Probability is the foundation of statistics, machine learning, quantum mechanics, and decision theory. Understanding it changes how you think about evidence, risk, prediction, and uncertainty itself.

Every claim about data—this drug works, this model predicts, this pattern is real—rests on probability. Master the mathematics and you see through the fog of uncertainty to what can actually be concluded.


This is the hub page for the Probability series. Start with "What Is Probability?" for the journey from frequentist coin flips to the mathematics that makes rational belief possible.

The Series

What Is Probability? Quantifying Uncertainty
Probability measures how likely events are - from 0 impossible to 1 certain
Basic Probability Rules: And Or and Not
Probability rules combine events - P(A and B) P(A or B) and P(not A)
Conditional Probability: When Information Changes the Odds
Conditional probability updates likelihood given new information
Bayes' Theorem: Updating Beliefs with Evidence
Bayes' theorem inverts conditional probability - how evidence should change your mind
Random Variables: Numbers That Depend on Chance
Random variables assign numbers to outcomes - discrete or continuous
Expected Value: The Long-Run Average
Expected value is the weighted average outcome
Variance and Standard Deviation: Measuring Spread
Variance measures spread from the mean - standard deviation is its square root
The Normal Distribution: The Bell Curve and Why It Appears Everywhere
The normal distribution emerges from many small random effects
Common Distributions: Binomial Poisson and Beyond
Different situations have different distributions - binomial for coin flips Poisson for rare events
The Law of Large Numbers: Why Averages Stabilize
More trials means the average converges to expected value
The Central Limit Theorem: Why the Bell Curve Rules
Sums of random variables become normal - the most important theorem in statistics
Synthesis: Probability as the Logic of Uncertainty
Probability is consistent reasoning under uncertainty