Description
Subtract cohortIndex from periodIndex using exact integer intermediates before numeric export.
Longitudinal ageing research links observations to people, waves, and sources. A person may appear in multiple records, so distinct-person coverage and record counts answer different questions and require explicit duplicate rules.
Subtract cohortIndex from periodIndex using exact integer intermediates before numeric export.
When to use this tool
Use Cohort Period Index Gap when you need a record-coverage or source-support diagnostic in ageing research.
How to use the tool and how it works
- Enter cohortIndex, periodIndex. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read indexGap. Use the output convention below.
Subtract cohortIndex from periodIndex using exact integer intermediates before numeric export.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| cohortIndex | Cohort Index | Required. Safe integer. |
| periodIndex | Period Index | Required. Safe integer. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| indexGap | Index Gap | Required. Safe integer. |
{
"input": {
"cohortIndex": 10,
"periodIndex": 15
},
"output": {
"indexGap": 5
}
}Limitations and assumptions
- Indexes use a supplied common origin and scale; their gap does not identify age, verify a cohort, or solve age-period-cohort effects.
- 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
Review the original study design, identifiers, and missing-data definitions. Use the full longitudinal dataset for inference rather than treating a local coverage flag as evidence of representativeness.
References
Similar or alternative tools
- Cohort Age Period Birth Year Identity
Return periodYear-ageYears and subtract recordedBirthYear for identityResidual.
- Pension Study Birth Cohort Index
Floor (birthYear-originYear)/cohortWidth for cohortIndex and return the corresponding lower year and excluded upper year.