55. Specifically, it is equal to σ √t, where σ is the stock’s volatility estimate for the period, and t is the length in years of the redemption notice period. As a numerical illustration, if t is one month, the short term volatility estimate is 0.30 per annum, and absent any jumps, the stock is expected to move 0.30 × √ (1/12) = 0.866, that is, ±8.66% in one month with a probability of 68%. The two standard deviation, or equivalently, a 95% confidence interval implies a call delay of 2 × 8.66 = 17.32% above the effective conversion price, assuming a log-normal return distribution for the stock price.