Find an intersection probability from a marginal and conditional rate, an explicit independence assumption, or a joint count.
How to use this tool
- Choose the event or model and review the assumptions below.
- Enter the labeled inputs. Probability inputs are percentages from 0 to 100, not decimal fractions.
- Select Calculate and read the labeled outputs.
- Change an input and calculate again; Reset restores the example inputs.
Calculation method
P(A∩B)=P(A)P(B|A). Under independence only, P(A∩B)=P(A)P(B). From counts, P(A∩B)=joint count/total.
Assumptions and limits
Computes the intersection from an explicit model. Independence must be justified; marginal probabilities alone do not identify a general joint probability.
Worked example
Starting at P(A)=40% and P(B|A)=30%, the intersection is 12%. Count mode with 12 shared cases among 100 observations produces the same result.
Worked reading and practical questions
- Joint Probability in Dependent Draws: Update the Second Factor
- Joint Counts and Conditional Counts Use Different Denominators
Browse Statistics calculators or explore other tools on the GreenCalc homepage.
Frequently asked questions
What does this calculator assume?
Computes the intersection from an explicit model. Independence must be justified; marginal probabilities alone do not identify a general joint probability.
How do I enter and update the inputs?
Use the labeled fields, then select Calculate. Percent fields use 0 to 100. After editing, calculate again; Reset restores the example inputs.