data/mathematical/53.mml
<math xmlns='http://www.w3.org/1998/Math/MathML' display='inline'><semantics><mrow><mi>E</mi><mrow><mo>[</mo><msup><mover><mi>σ</mi><mo stretchy="false">^</mo></mover> <mn>2</mn></msup><mo>]</mo></mrow><mo>=</mo><mfrac><mrow><mi>n</mi><mo>−</mo><mn>1</mn></mrow><mi>n</mi></mfrac><msup><mi>σ</mi> <mn>2</mn></msup></mrow><annotation encoding='application/x-tex'>E \left[ \hat{\sigma}^2\right] = \frac{n-1}{n} \sigma^2</annotation></semantics></math>