Description
Return incidence×duration and prevalence-minus-product residual.
Epidemiological model terms link supplied prevalence, rates, durations or risk ratios under explicit assumptions. A mathematical identity or approximation does not estimate those inputs or establish the causal effect of an exposure.
Return incidence×duration and prevalence-minus-product residual.
When to use this tool
Use Prevalence Incidence Duration Residual when you need one transparent population-level model term.
How to use the tool and how it works
- Enter prevalence, incidencePerTime, meanDuration. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read approximatePrevalence, residual. Use the output convention below.
Require prevalence in [0, 1] and nonnegative incidencePerTime/meanDuration. Return incidence×duration and prevalence-minus-product residual.1
Prevalence depends on both incidence and disease duration. The product evaluated here is a limited approximation, not a general conversion between arbitrary surveillance measures.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| prevalence | Prevalence | Required. Finite number; minimum 0; maximum 1. |
| incidencePerTime | Incidence Per Time | Required. Finite number; minimum 0. |
| meanDuration | Mean Duration | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| approximatePrevalence | Incidence rate times mean duration; may exceed one under supplied inputs. | Required. Finite number. |
| residual | Residual | Required. Finite number. |
{
"input": {
"prevalence": 0.1,
"incidencePerTime": 0.02,
"meanDuration": 4
},
"output": {
"approximatePrevalence": 0.08,
"residual": 0.020000000000000004
}
}Limitations and assumptions
- Incidence rate and duration use reciprocal time units. P≈I×D is a limited low-prevalence steady-state approximation; the product can exceed one and is not a probability estimate guaranteed valid by the tool.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use an appropriate epidemiological study and causal analysis for interpretation. Check steady-state assumptions, confounding, exposure definitions, compatible time units and uncertainty before applying a model term to health policy or individual care.
References
Similar or alternative tools
- Population Attributable One Exposure Term
Return prevalence×(risk-1) divided by that denominator.
- Recurrent Episode Washout Gap Tool
Compare an explicit interepisode time gap with a supplied inclusive washout duration without defining recurrent disease episodes.