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NISM Certifications · NISM-Series-X-A: Investment Adviser (Level 1) · Introduction to Modern Portfolio Theory

A two-asset portfolio has 50% in X (standard deviation 20%) and 50% in Y (standard deviation 20%). If the correlation between X and Y is -1, what is the portfolio standard deviation?

The portfolio standard deviation is 0%. With perfect negative correlation and equal weights in two equally volatile assets, the movements offset completely, so variance works out to 100 plus 100 minus 200, which is zero.

  1. A20%
  2. B10%
  3. C0%Correct
  4. D40%

Explanation

Variance = w1²s1² + w2²s2² + 2w1w2 rho s1 s2 = 0.25x400 + 0.25x400 + 2x0.25x(-1)x400 = 100 + 100 - 200 = 0. So standard deviation is 0%. With correlation +1 it would be 20%, which is the weighted average and the distractor for ignoring diversification.

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