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Question 7 (Bonus 1pt: Variance estimate) Let ri for i=1,,n be independent sample of return r, a random variable with mean r and variance 2. Define the estimates r^=n1i=1nri,s2=n11i=1n(rir^)2. Show that E[s2]=2, i.e. s2 is an unbiased estimate of 2. Note that you should calculate E[n11i=1n(rir^)2] with r^=n1i=1nri being random. Question 7 (Bonus 1pt: Variance estimate) Let ri for i=1,,n be independent sample of return r, a random variable with mean r and variance 2. Define the estimates r^=n1i=1nri,s2=n11i=1n(rir^)2. Show that E[s2]=2, i.e. s2 is an unbiased estimate of 2. Note that you should calculate E[n11i=1n(rir^)2] with r^=n1i=1nri being random