Extension card · Z-Number
Spherical Fuzzy Z-Number MARCOS (Niu, 2024)
This is the form of MARCOS for situations where criterion values are given as spherical fuzzy triples (support, rejection, hesitancy), and each of these three degrees is further accompanied by its own reliability. The output is again a final utility degree and a rank.
Base method
MARCOS →
Philosophy, mechanics, strengths and weaknesses are on the base method card; this card describes only the difference.
Data type (family)
Z-Number →
What this data type is, when to use it, how to write it in a cell: the family's full account is here.
What Changes from the Base Method?
Four things change; the extended-table and ideal/anti-ideal-ratio logic does not.
Cells. In crisp MARCOS every cell is a single number. Here every cell consists of six numbers: a support (ε), rejection (ν) and hesitancy (∂) degree for a judgement, with the sum of the squares of all three not exceeding 1, as in the spherical fuzzy structure; each of these three degrees is further accompanied by its own reliability (τ_ε, τ_ν, τ_∂). Weights are taken from outside; DecisionMind typically chains them in from the Spherical Fuzzy Z-Number CRITIC card. The method supports group decisions: several experts' matrices can be merged, with expert weights, into a single collective matrix.
Scale equalisation. Crisp MARCOS ratios the benefit column to the ideal and the cost column to its inverse. Here there is no division; for a cost criterion, the support-hesitancy pair swaps places (ε,τ_ε is exchanged with ∂,τ_∂), exactly as in the SFZN-CRADIS extension.
PIS/NIS and the closeness coefficient. This is where the extension parts ways with CRADIS. SFZN-CRADIS builds a SINGLE ideal and a SINGLE anti-ideal point for the whole decision matrix, sums the distances, and takes a single ratio only at the very end. Here a separate PIS (positive ideal) and NIS (negative ideal) are built for each criterion; every cell's distance to the PIS and NIS is computed over value×reliability products, and is reduced immediately, cell by cell, to a closeness coefficient. The six-number cell collapses into a single crisp number, per criterion, before it ever enters MARCOS's extended table.
Extended table and final utility degree. Crisp MARCOS's extended table (with its anti-ideal and ideal rows) is built on top of these closeness coefficients. The table is normalised and weighted, ratioed to the ideal and the anti-ideal (U+, U−), and Stević's (2020) canonical utility function gives the final utility degree.
Reliability's contribution is real only when it differs across alternatives. This has been verified by this card's author running the kernel directly: when an alternative's reliability on ONE criterion is lowered, the final utility degree and the rank genuinely change; as the illustrative example below shows, this difference can be large enough to reverse the ranking. This runs in the same direction as the finding already reported on the SFZN-CRADIS card; both extensions genuinely read reliability.
DecisionMind fixes the PIS/NIS logic, the closeness coefficient and MARCOS's canonical final-utility function for this extension.
How to Read the Output
The final utility degree is read exactly as in crisp MARCOS: a position relative to this set's own ideal and anti-ideal references (see the MARCOS card). The difference is here: this degree passes through a distance calculation that carries, separately for every criterion, both the judgement itself and its reliability. Two alternatives sharing the same support-rejection-hesitancy triple need not share the same final utility degree; the reliability difference also comes into play.
Thus instead of writing:
"In spherical fuzzy Z-number MARCOS, reliability is purely indicative and does not change the result"
the report should read:
"Reliability genuinely enters the calculation here; which alternative relies on a lower-reliability source on which criterion should be stated separately in the report"
When to Prefer This over the Base Method
When an expert's judgement is given both as a support-rejection-hesitancy triple and with a separate reliability attached to each degree of that triple. The typical case is one where several assessors (a student survey, peer review, a manager's observation, say) contribute to the same judgement from sources of differing reliability, and this difference needs to be reflected in the calculation. The data-collection burden is heavy (six numbers per cell); it should only be taken on where a genuine reliability difference will actually affect the decision. Where hesitancy is not separately measured, or where every source shares the same reliability, the Spherical Fuzzy data-type card may point to a simpler extension. Crisp MARCOS's exit condition applies here too: where no compromise is acceptable on one criterion, this extension remains compensatory as well.
Mistakes Specific to This Extension
Confusing this card with SFZN-CRADIS. Both use the same six-number cell, but SFZN-CRADIS sums distances against a SINGLE global ideal/anti-ideal point and only takes a ratio at the very end; this card builds a separate PIS/NIS per criterion and descends to an early, cell-level closeness coefficient. The two engines follow a different step order and produce different numbers.
Forgetting that the closeness coefficient is an early defuzzification. The six-number cell collapses to a single crisp number before it ever enters the extended table; past this point, which component (support or reliability) is driving the result is no longer separately visible.
Writing the same reliability into every cell and claiming "a Z-number was used". If reliability does not differ at all across alternatives, it carries no discriminating information.
Treating reliability as a separate additive term. The distance formula uses the products (ε×τ_ε), (ν×τ_ν), (∂×τ_∂); feeding ε and τ_ε separately into a squared difference gives a wrong distance.
The governing principle is this:
Reliability changes the final utility degree only when it genuinely differs across alternatives; which alternative relies on a lower-reliability source on which criterion should be stated separately in the report.
Cases
The first case is anchored to Niu's (2024) case study on evaluating English-teacher performance (four teachers, four criteria); it processes the same input table as the [SFZN-CRADIS](../sfzn-cradis.md) card through a different engine (MARCOS). The second case is an illustrative construction.
1. Illustrative example (anchored to a source): Assessing four teachers' performance (Niu, 2024)
A school's English department has assessed four teachers (T1–T4) on four criteria: lesson-planning skill, classroom management, student feedback and professional-development engagement. All four are "higher is better." In this example the rejection degree is zero and the reliability degrees are set to one; only the support and hesitancy degrees vary. Weights are chained in from Spherical Fuzzy Z-Number CRITIC.
| Teacher | Y1 (support; hesitancy) | Y2 | Y3 | Y4 |
|---|---|---|---|---|
| T1 | 0.517; 0.461 | 0.577; 0.451 | 0.511; 0.709 | 0.378; 0.467 |
| T2 | 0.378; 0.439 | 0.476; 0.539 | 0.378; 0.423 | 0.366; 0.439 |
| T3 | 0.697; 0.366 | 0.584; 0.468 | 0.533; 0.524 | 0.503; 0.342 |
| T4 | 0.552; 0.370 | 0.570; 0.470 | 0.539; 0.341 | 0.322; 0.311 |
| Direction | higher is better | higher is better | higher is better | higher is better |
| Weight | 0.18 | 0.26 | 0.36 | 0.20 |
The method builds a PIS and NIS for each criterion, computes every cell's distance to these two points over value×reliability products, and reduces this to a closeness coefficient. The extended table is built on these coefficients, normalised and weighted, and the final utility degree (U) is calculated.
| Teacher | Final utility degree (U) | Rank |
|---|---|---|
| T3 | 0.8100 | 1 |
| T4 | 0.7821 | 2 |
| T1 | 0.4681 | 3 |
| T2 | 0.2760 | 4 |
The result reads as follows. T3 sits relatively close to the PIS on all four criteria and is strong on Y3, the most heavily weighted criterion; T4 follows close behind. T1 and T2 sit in the rearward ranks.
An important disclosure is needed here: the final utility degrees above (0.8100; 0.7821; 0.4681; 0.2760) were obtained by independently recomputing this table with today's DecisionMind engine, and the engine's ranking matches the order reported in the paper (T3>T4>T1>T2). But the engine's own internal verification gate reports that these values do not exactly match the numbers recorded in the manifest (T1=0.700; T2=0.550; T3=0.696; T4=0.507); the manifest's numbers are themselves derived from the paper's own Table XXIV/XXV values, not from the engine recomputing this table from scratch (from the Table IV/V input). This has been recorded as a separate finding (see the verification notes); a similar difference has also been reported on the SFZN-CRADIS card.
The board's hesitation is this: what would happen if T3's assessment on all four criteria rested only on the teacher's own self-report, without an external observer's confirmation? That is, if reliability were low on all four criteria. This scenario has been recomputed in Python using the engine's own algorithm. When T3's reliability on all four criteria is lowered from 1.0 to 0.4, the ranking genuinely changes: T4 (0.9063) moves to first place, T1 (0.7192) second, T2 (0.6522) third, and T3 (0.3232) drops to last. By contrast, something different happens if only T3's reliability on a single criterion (Y3) is lowered by the same proportion. T3 drops from first to second place (T4 becomes first at 0.7762, T3 second at 0.7251), not to last. This shows that whether reliability is lowered generally (consistently low across all criteria) or locally (low on a single criterion) changes the outcome.
In the report: "T3 obtained the highest final utility degree in the current assessment (0.8100); but this advantage rests on the reliability of T3's assessment across all four criteria. If reliability is lowered on all four criteria together, T3 drops to last; if it is lowered on only one criterion, T3 falls to second place, so the source of T3's assessment should be stated separately in the report."
Source: Niu (2024), IJACSA 15(3), Tables IV–V (input); a ranking matching the paper's order (T3>T4>T1>T2) has been produced by today's independent engine recomputation, but the magnitude of the final utility degrees does not match the numbers recorded in the manifest (detail in the verification notes). The reliability sensitivity scenario was independently computed by this card's author.
2. Childcare: A nursery chain's assessment of care-giving staff
A nursery chain will carry out the annual performance assessment of four care-giving staff. Criteria: child-safety practice, parent communication, daily activity planning and emergency-response knowledge; all four are "higher is better." For each staff member, both the nursery director and a parent representative give support, rejection and hesitancy degrees separately; the chain merges these two views into a single collective assessment. Reliability is derived from how many months each assessor has been observing that staff member: high for long-standing observers, low for those who have only just started.
The method computes each staff member's distance from their spherical fuzzy Z-numbers to the PIS and NIS, reduces this to a closeness coefficient, normalises and weights it in the extended table, and finds the final utility degree. Suppose the result places a staff member who is very strong on child safety but weak on parent communication first, and a staff member who is moderate but consistent across all four criteria second.
The chain's hesitation is this: the first-ranked staff member's child-safety score was recorded with low reliability, because this staff member started recently. If reliability were raised, the first rank might not change, but if it were lowered, the second-ranked staff member could move ahead. The chain should test this sensitivity before basing an annual bonus decision on the reliability of a single assessment period.
In the report: "The staff member who stands out on child safety is first in the current assessment; but the assessment on this criterion rests on a low-reliability (recently started) source, and a bonus decision should not be made before this reliability is confirmed."
3. What Not to Do
In the illustrative example, lowering T3's reliability on only one criterion and reporting "overall reliability was lowered, so T3 dropped to last" is wrong: when lowered on a single criterion, T3 drops to second, not last; it drops to last only when lowered on all four criteria together. The second error is reporting the manifest's numbers (such as T1=0.700) as though they were today's engine output; the engine's ranking matches these numbers in direction but not in magnitude. The third error is comparing this card's result directly against SFZN-CRADIS's result; although the two engines use the same cell format, they follow a different step order (a single ideal/anti-ideal sum versus a cell-level PIS/NIS closeness coefficient).
Sources
For the formulas behind each step, the intermediate tables and citation formats, see the DecisionMind method page: decisionmind.app/library/sfzn-marcos
Niu, J. (2024). Spherical Fuzzy Z-Numbers-based CRITIC CRADIAS and MARCOS Approaches for Evaluating English Teacher Performance. International Journal of Advanced Computer Science and Applications, 15(3), 1153–1166. DOI: 10.14569/IJACSA.2024.01503115
Stević, Ž., Pamučar, D., Puška, A., & Chatterjee, P. (2020). Sustainable supplier selection in healthcare industries using a new MCDM method: Measurement of Alternatives and Ranking according to Compromise Solution (MARCOS). Computers & Industrial Engineering, 140, 106231. DOI: 10.1016/j.cie.2019.106231
Kutlu Gündoğdu, F., & Kahraman, C. (2019). Spherical fuzzy sets and spherical fuzzy TOPSIS method. Journal of Intelligent & Fuzzy Systems, 36(1), 337–352. DOI: 10.3233/JIFS-181401
Zadeh, L. A. (2011). A note on Z-numbers. Information Sciences, 181(14), 2923–2932. DOI: 10.1016/j.ins.2011.02.022