Measures spread/variability of data. Used everywhere in ML: normalization, evaluation, monitoring.
variance = (1/n) × Σ(x_i - μ)²std = √variancestd([2,4,4,4,5,5,7,9]) → 2.0
Round to **5 decimal places**.
Similar Problems
Test Cases (2 visible · 2 hidden)
Case 1: Classic example
Input: std([2,4,4,4,5,5,7,9])
Expected: 2.0
Case 2: No variation
Input: std([5,5,5,5])
Expected: 0.0
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