条件付き確率計算機

共有リンク

はじめに

Conditional Probability Calculator — Compute P(A|B) from P(A and B) and P(B). Enter P(A and B), P(B) to get an instant, accurate result.

計算式

P(A|B) = P(A and B) / P(B), the probability of A given that B has occurred.

ステップごとの説明

Enter the P(A and B).
Enter the P(B).
Click Calculate to see your result instantly.

実例

Example: With P(A and B) = 0.2, P(B) = 0.5, the Conditional Probability Calculator gives P A Given B: 0.4.

よくある質問

What if P(B) is zero?

Conditional probability is undefined when P(B) = 0, since an event with zero probability cannot be conditioned on.

How is this different from P(A and B)?

P(A and B) is the probability both happen out of all possible outcomes; P(A|B) narrows the sample space to only outcomes where B already happened.

What inputs does the Conditional Probability Calculator need?

You'll need to provide: P(A and B), P(B). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.

How accurate is the Conditional Probability Calculator?

The Conditional Probability Calculator applies the formula exactly as calculated — P(A|B) = P(A and B) / P(B), the probability of A given that B has occurred. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.

Is the Conditional Probability Calculator free to use?

Yes, the Conditional Probability Calculator is completely free, requires no signup, and runs instantly in your browser.