CHAPTER 25Statistical and Theoretical Concepts

This chapter provides a brief introduction to concepts in statistics and portfolio theory. We include a fair amount of math, but we do our best to avoid excessive complexity. Our intent is to establish a sufficient foundation for this book that is reasonably clear, but this review is by no means comprehensive. We therefore include references to other sources that provide a more thorough and technical treatment of these topics.

DISCRETE AND CONTINUOUS RETURNS

We define the discrete return upper R Subscript t for an asset from time t minus 1 to t as the change in price over some period plus any income generated, all divided by the price at the beginning of the period:

(25.1)upper R Subscript t Baseline equals StartFraction upper P Subscript t Baseline minus upper P Subscript t minus 1 Baseline plus upper I Subscript t Baseline Over upper P Subscript t minus 1 Baseline EndFraction

Next, we denote the log return of the asset using a lowercase r Subscript t:

(25.2)r Subscript t Baseline equals ln left-parenthesis 1 plus upper R Subscript t Baseline right-parenthesis

Here, ln left-parenthesis x right-parenthesis is the natural ...

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