Information Coefficient (Spearman) - Quant Researcher Interview Question

Problem Description

The Information Coefficient (IC) is a pivotal metric in quantitative finance for assessing the predictive power of a trading signal relative to realized returns. While Pearson correlation assumes linearity, the Spearman rank correlation is often preferred for its ability to capture monotonic relationships and its robustness to outliers common in financial data. Task Implement a function solution(signals, returns) that calculates the Spearman Information Coefficient between a list of trading sig