Attrition-Adjusted Final N Calculator
Conditional expectedfinalN=enrolled×(1−attrition), fractional expectation retained, not deterministic integer participant outcome or inverse recruitmentbudget. Actual independently qualified instrument/cohort/matching units; no diagnosis, causal outcome, validated personal prediction or universal clinical cutoff.
Description
Expected final sample size reduces enrollment by a proposed attrition fraction.
Expected final sample size reduces enrollment by a proposed attrition fraction.1
A fractional expectation does not determine how many participants will actually remain. The calculation and input requirements are explained below.
When to use Attrition-Adjusted Final N Calculator
Enter integer initial enrollment 0–1000000 and attrition fraction 0–1.
How to use Attrition-Adjusted Final N Calculator and how it works
- Prepare the measurements or independently established model inputs described below, with matching units and observation scope.
- Enter the required fields and run Attrition-Adjusted Final N Calculator.
- Read the result fields using the formula, output units, signs and ordering explained below.
- Correct any rejected inputs and rerun; interpret the result within the stated model and its assumptions.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| actualInitiallyEnrolledCount | Actual Initially Enrolled Count. Use the units and matching context stated in the calculation below. | number | Required; integer 0–1000000; finite; other constraints below |
| callerIndependentlyAssessedAttritionFraction | Caller Independently Assessed Attrition Fraction. Use the units and matching context stated in the calculation below. | number | Required; fraction from 0 to 1; finite; other constraints below |
Enter integer initial enrollment 0–1000000 and attrition fraction 0–1. Multiply enrollment by one minus attrition. Return the fractional expected size without rounding or predicting individual retention.
expectedFinalN=initialN*(1-attritionFraction) Apply the input ordering, units and branch conditions stated above.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the calculated or selected fields below. | object |
| result.value | Numeric result under the formula and output units explained above. | number |
{
"input": {
"actualInitiallyEnrolledCount": 100,
"callerIndependentlyAssessedAttritionFraction": 0.2
},
"output": {
"result": {
"value": 80
}
}
}Limitations and assumptions
The calculation uses the supplied observations and model inputs. It does not collect measurements, select a reference population or coefficient, or establish that the model applies to the actual case. The stated branch conditions and output units remain part of the result.
All fields require explicit values. Unexpected fields, wrong types, nonfinite numbers and sparse arrays are rejected. Alignment, bounds and supported-token rules are explained above; extremely large inputs or nonfinite results can also fail. Input errors differ from successful false comparisons, unavailable-domain flags and empty match lists.
Alternative or Complementary methods
Use Independent t-Test Power .80 Sample Size for a complementary operation: Two-group power planning requires a proposed effect and significance level.
Use SEM Minimum Sample 10-Per-Parameter Rule for a complementary operation: A participants-per-parameter heuristic is a nominal planning budget.
References
-
Attrition-Adjusted Final N Calculator — tool.io
Similar or alternative tools
- Independent t-Test Power .80 Sample Size
Two-group power planning requires a proposed effect and significance level.
- SEM Minimum Sample 10-Per-Parameter Rule
A participants-per-parameter heuristic is a nominal planning budget.