Geology Kurtosis Folk Ward Calculator
Folk–Ward tail/interquartile PHI spread ratio, not moment kurtosis. Caller independently establishes matching units, evidence, method edition and applicability; output is not compliance, diagnosis, work-safety approval, geological identity or validated hazard prediction.
Description
Folk–Ward graphic kurtosis compares tail spread with central spread on the phi grain-size scale.
Folk–Ward graphic kurtosis compares tail spread with central spread on the phi grain-size scale.1
It summarizes a percentile relationship rather than computing a fourth statistical moment from every grain observation. Use this tool to calculate kurtosis folk ward from the supplied measurements and assumptions.
When to use Geology Kurtosis Folk Ward Calculator
Use this tool to calculate kurtosis folk ward from the supplied measurements and assumptions. Establish the measurement units, sampled interval, calibration or model edition and geological assumptions before entering data.
How to use Geology Kurtosis Folk Ward Calculator and understand its results
- Establish the measurement units, sampled interval, calibration or model edition and geological assumptions before entering data.
- Enter phi5, phi25, phi75, phi95, using the field meanings and rules below, then run the tool.
- Read graphicKurtosis. Interpret the fields using their units, signs and evidence conventions below.
- If input validation fails, correct the reported field and run again. Before applying the result, check reference scope, model assumptions and any missing evidence or placeholder values.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| phi5 | Phi5 | number | Required |
| phi25 | Phi25 | number | Required |
| phi75 | Phi75 | number | Required |
| phi95 | Phi95 | number | Required |
Enter nondecreasing phi5, phi25, phi75 and phi95, requiring phi75>phi25. Divide the outer spread by 2.44 times the central spread. No percentile derivation, moment-based kurtosis or interpretation category is supplied.
graphicKurtosis=(phi95−phi5)/[2.44×(phi75−phi25)] Use the exact units, boundary rules, ordering and missing-evidence conventions above.
| Output field | Meaning | Value type |
|---|---|---|
| graphicKurtosis | Graphic Kurtosis; follow the units, sign, ordering and evidence convention stated above | number |
{
"input": {
"phi5": -2,
"phi25": -1,
"phi75": 1,
"phi95": 2
},
"output": {
"graphicKurtosis": 0.819672131147541
}
}Limitations and assumptions
It summarizes a percentile relationship rather than computing a fourth statistical moment from every grain observation. Interpretation depends on the units, sampling scope and exact model described above.
All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse evidence arrays fail validation; the specific bounds and alignment requirements are stated above. Extremely large inputs or outputs can also be rejected. An input error is distinct from a successful result reporting false, no matches or missing evidence.
Alternative or Complementary methods
Use Geology Wentworth Phi To Mm Calculator for this related task: The phi grain-size scale is logarithmic, with increasing phi corresponding to decreasing diameter.
Use Geology Wentworth Grain Size Phi Calculator when its separate inputs and assumptions fit the question: A phi value is the negative base-two logarithm of grain diameter measured in millimeters.
References
-
Geology Kurtosis Folk Ward Calculator — tool.io
Similar or alternative tools
- Geology Wentworth Phi To Mm Calculator
The phi grain-size scale is logarithmic, with increasing phi corresponding to decreasing diameter.
- Geology Wentworth Grain Size Phi Calculator
A phi value is the negative base-two logarithm of grain diameter measured in millimeters.