Relative Risk Calculator
Calculates the ratio of risks between two groups. The form displays risk1/risk0 beside relative risk, using a worked condition that can be recalculated with the labeled inputs.
Set the labeled inputs
Relative Risk
Purpose of this relative risk calculation
The relative risk page calculates the ratio of risks between two groups.
Relative Risk is limited to the statistical quantity named by the result panel. The relative risk calculation does not silently add a population, time horizon, causal direction, or decision threshold that is absent from the fields.
Reading the relative risk fields
- Risk in exposed group: For relative risk, the worked value for risk in exposed group is 0.2 risk. Treat the risk in exposed group entry (0.2 risk) explicitly as a count, proportion, rate, estimate, or model parameter before comparing relative risk conditions. The form enforces minimum 0, maximum 1.
- Risk in comparison group: For relative risk, the worked value for risk in comparison group is 0.1 risk. Treat the risk in comparison group entry (0.1 risk) explicitly as a count, proportion, rate, estimate, or model parameter before comparing relative risk conditions. The form enforces minimum 0, maximum 1.
The entries used for relative risk must refer to one coherent analysis condition. Combining incompatible populations, periods, or measurement definitions can produce valid relative risk arithmetic for a nonexistent study.
From inputs to relative risk
For relative risk, match every symbol in the relationship to a labeled field before substituting numbers. Relative Risk is reported in the scale implied by the inputs and formula.
While checking relative risk, inspect every denominator in risk1/risk0. For relative risk, a zero or near-zero denominator can make relative risk undefined or unstable.
Worked values for relative risk
The default relative risk condition is Risk in exposed group = 0.2 risk, Risk in comparison group = 0.1 risk.
Risks .20 and .10 give relative risk 2.
The live calculator reports Relative risk 2. Repeating one intermediate step from risk1/risk0 provides a fixed relative risk reference check for later code changes.
Assumptions behind relative risk
Relative risk should be paired with an absolute risk difference and a clearly defined follow-up interval.
For relative risk, diagnostic and risk measures are conditional on named denominators, reference definitions, population prevalence, and follow-up time.
Reading relative risk in context
When interpreting relative risk, keep the two-by-two counts or source risks with the result; a ratio alone can hide very different absolute event frequencies.
As a second check for relative risk, reversing the numerator and denominator answers a different question, so retain the direction printed in risk1/risk0.
A practical stress test for relative risk
Change risk in exposed group while holding the remaining entries fixed, then state why the direction and size of the relative risk change are plausible from risk1/risk0.
Repeat the relative risk exercise with risk in comparison group. If a modest defensible change materially alters the interpretation, report both conditions rather than presenting that relative risk scenario as exact.
The surrounding workflow may also require attributable fraction among exposed.
Mistakes to avoid in the relative risk setup
Before accepting relative risk, compare every entered value with its label, unit, and allowed domain after reading the printed relationship from left to right.
For relative risk, do not move a number between fields merely because the units look compatible; each label gives the number a different statistical role.
Another relative risk failure occurs when a rounded output is reused as though it were the original measurement. Carry guard digits through calculations that depend on relative risk, then round only the reported value.
What to record with relative risk
Report relative risk using risk1/risk0, followed by the entered values, units, exclusions, and analysis date. Name the relative risk population or dataset boundary instead of leaving it implicit.
Keep the full calculator output with the record, including Relative risk 2. A later relative risk review can then distinguish a changed input from a different convention or software implementation.
Questions about relative risk
How should relative risk be rounded?
Keep the unrounded relative risk for subsequent arithmetic, then report only the precision supported by the source measurements and the decision context. Extra digits in relative risk do not correct sampling or model error.
Which input deserves the closest boundary check?
For relative risk, start with risk in comparison group and then risk in exposed group. Confirm the relative risk units and allowed domain because a valid-looking entry can still describe the wrong statistical setup.
Why could another program report a different relative risk?
A different convention for rounding, tails, ties, interpolation, parameterization, or missing values can change relative risk. Compare the printed relative risk formula and its input definitions before treating either output as wrong.
What does relative risk represent on this page?
It is the quantity produced by risk1/risk0 from the displayed risk in exposed group, risk in comparison group. This page calculates the ratio of risks between two groups.