In this study a two-part mixed probability density function was derived which described the relative changes in the Standard and Poor's 100 Stock Index over various intervals of time. The density function is a mixture of two different halves of normal distributions. Optimal values for the standard deviations for the two halves and the mean are given. Also, a general form of the function is given which uses linear regression models to estimate the standard deviations and the means. The density functions allow stock market participants trading index options and futures contracts on the S & P 100 Stock Index to determine probabilities of success or failure of trades involving price movements of certain magnitudes in given lengths of time.

The purpose of this research was to determine if presentation format, given a particular task to be performed, would affect the decision-making process of financial decision makers. The problem motivating this study is the potential for managers to make inefficient decisions when they use reports which are presented inappropriately for a given task.