CFA CFA Level 1 Question of the Week – Portfolio Management

Question of the Week – Portfolio Management

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    • Avatar of strugglerstruggler
      Participant
        • Undecided
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        5
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        I got confused…  anyone, could tell the general formula of portfolio standard deviation ??? thanks 🙂

      • Avatar of Stuj79Stuj79
        Participant
          • CFA Charterholder
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          4
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          Yup, this is a bread and butter calculation in terms of CFA exams…everyone should make sure they know how to calculate this, and also why it is calculated this way. Knowing why, as well as how will stand you in good stead.

        • Avatar of AdaptPrepAdaptPrep
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            • Undecided
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            The portfolio standard
            deviation formula is:

             

            (sigma_p)^2 = (w_1)^2 *
            (sigma_1)^2 + (w_2)^2 * (sigma_2)^2 + 2(w_1)(w_2) * Cov(R_1, R_2)

             

            We have:

            w_1 = 15,000 / 20,000 = 0.75

            w_2 = 5,000 / 20,000 = 0.25

            sigma_1 = 0.3

            sigma_2 = 0.1

            Cov(R_1, R_2) = 0.05

             

            Therefore,

            (sigma_p)^2 = (0.75^2)(0.3^2)
            + (0.25^2)(0.1^2) + 2(0.75)(0.25)(0.05) = 0.07

            sigma_p = (0.07)^0.5 = 0.2645

          • Avatar of rsparksrsparks
            Participant
              • CFA Level 2
              Up
              3
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              I would also highlight the interaction between correlation, beta, variance and standard dev. I had the below all on one card:

              correlation (p)  = Cov1,2 / (sigma_1) (sigma_2)

              Beta (b) = Cov1,2 / Variance_market

              Beta (b) = (p) (sigma_1) / Sigma_market

              The above mentioned formula: (sigma_p)^2 = (w_1)^2 *
              (sigma_1)^2 + (w_2)^2 * (sigma_2)^2 + 2(w_1)(w_2) * Cov(R_1, R_2)

              I passed level 1 last year and still remember these formulas. I had this index card stock to my monitor at work. I had other cards stuck in the bathroom, on my desk for when I got up in the morning, etc. Hopefully this will help some of you too 🙂

            • Avatar of googs1484googs1484
              Participant
                • CFA Level 3
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                2
                ::

                Darn haha. Tried doing the math in my head. I’ll stick to the BA2 going forward lol.  

              • Avatar of aaronpcjbaaronpcjb
                Participant
                  • CFA Level 1
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                  0
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                  Stupidly misread ‘covariance’ as ‘correlation’ and multiplied it by the standard deviations. 

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