Spearman-based correlation methods under single-valued neutrosophic sets with application to wheat farmland selection

Wheat remains a main staple crop in Sub-Saharan Africa, yet its cultivation is increasingly endangered by climate unpredictability and environmental uncertainty. The selection of an appropriate farmland for optimal wheat productivity, therefore, involves complex, imprecise, incomplete, and uncertain information. In response to this problem, the proposed study employs the framework of single-valued neutrosophic sets, which has proven effective in modelling imprecision and indeterminacy in decision-making problems. Correlation coefficients under single-valued neutrosophic sets have been deployed to discuss complex selection problems with multi-criteria. Although some single-valued neutrosophic correlation coefficient measures have been established, a number of them lack appropriate statistical justification and reliability. This study introduces new correlation coefficient methods based on Spearman’s approach. The suggested methods are evaluated by comparing them to existing methods, and it is shown that they meet the requirements of the correlation coefficient while providing more accurate and reliable decision outcomes. In particular, based on the numerical experiment in Example 3.1, the two suggested correlation coefficient methods achieve accuracy percentages of 100% and 99.94% in Case I, and 100% and 89.23% in Case II—substantially outperforming the existing methods, which yield notably lower accuracy percentages in both cases. Their applicability is validated through a farmland selection problem aimed at maximizing wheat productivity, using data from a knowledge-based system. The framework is adaptable and can be extended to other complex decision-making scenarios.