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GATE 2020 ST – Question 43

Multivariate Analysis · Hotelling Tests and Correlation · 2 marks · Multiple choice

Two bivariate-normal populations have means(0,0),(1,1), common covariance $\begin{pmatrix}1&.5\\.5&1\end{pmatrix}$, equal priors and equal misclassification costs. For z₁=(.75,.75),z₂=(.25,.25), apply the linear discriminant rule.

  1. z₁→P₁,z₂→P₂
  2. z₁→P₂,z₂→P₁
  3. Both→P₁
  4. Both→P₂

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Show answer and explanation

Correct answer: (B) z₁→P₂,z₂→P₁

Explanation

With common covariance and equal priors, compare Mahalanobis distances or the linear discriminant difference. Symmetry puts the boundary at z₁coordinate+z₂coordinate=1. The point(.75,.75) has sum1.5 and is nearer mean(1,1);(.25,.25) has sum0.5 and is nearer(0,0). Thus B.

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