Probability Theory Fundamentals › Key Parameters

Michael BrenndoerferOctober 19, 20251 min read
Quantitative FinanceAll chapters
Part 1 of 15Mathematical Foundations
Chapter 2Probability Theory Fundamentals › Key Parameters
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The key parameters for simulating and analyzing financial returns are:

  • annual_return: Annualized arithmetic mean of iid daily simple returns (10% here), so the daily mean is 0.10/2520.10/252. It is not an exact target for the one-year compounded return, which under this model has expectation (1+0.10/252)252−1(1+0.10/252)^{252}-1.
  • annual_volatility: Annualized standard deviation under iid or zero-autocovariance scaling; daily volatility is the annual value divided by 252\sqrt{252}. This is the volatility convention for an additive sum of daily returns, not generally the exact standard deviation of a compounded annual simple return.
  • trading_days: Modeling convention for trading days per year (commonly 252). Exact counts vary by market and calendar year.
  • VaR confidence level: 95% and 99% are common choices, including the two used here. Higher confidence means more conservative risk estimates.
  • initial_price: Starting price for the simulation. All subsequent prices are computed relative to this value.