Risk difference interval calculator

Calculate difference estimate and 95% interval lower with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use difference estimate and 95% interval lower to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Exposed events a
20
Exposed non-events b
80
Control events c
10
Control non-events d
90
Difference estimate
0.1
95% interval lower
0.002002
95% interval upper
0.197998

Try another scenario

Exposed events a
21
Exposed non-events b
80
Control events c
10
Control non-events d
90
Difference estimate
0.107921
95% interval lower
0.009325
95% interval upper
0.206517
Calculation method

Calculation method

Difference estimate

Risk difference=pA-pB; unpooled 95% Wald interval, intentionally not clipped.

95% interval lower

Risk difference=pA-pB; unpooled 95% Wald interval, intentionally not clipped.

95% interval upper

Risk difference=pA-pB; unpooled 95% Wald interval, intentionally not clipped.

Symbols and units
a
Exposed events a
b
Exposed non-events b
c
Control events c
d
Control non-events d

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Assumptions & limits

Assumptions & limits

  • Large-sample descriptive interval; positive cells required, no automatic continuity correction. Supported limits: All required fields must be finite values of the exact declared type and within displayed bounds. Lists contain1–1000 finite numbers. JSON tables are numeric rectangular rows, at most100 rows and30 columns; individual tools have stricter shape/domain constraints. Large-sample descriptive interval; positive cells required, no automatic continuity correction.
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Further reading

Method reference ↗

Background reading; this does not imply endorsement or independent review of SumFizz.

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