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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 🙂