Why are there two types of stock price probability function?
The HoadleyProbAboveAtEnd function calculates the probability that at the end of a specified number of days the spot stock price will be above (or below) a target price. This is useful for seeing, for example, whether an European option is likely to be in the money at expiration. This function is available in both the trial and full versions of the add-in. The HoadleyProbAnyTime function calculates the probability that the stock price will exceed (or fall below) a target price at any time during the period. These probabilities are quite different from the “at end” probabilities and are extremely useful in evaluating American-exercise options — ie options that can be exercised at any time before expiration. As all equity options have American-style exercise this function is therefore of great value to most options traders as they need to understand the chances of target prices being reached before expiration as well as on expiration. This function is only available in the full version
