1. A computer-implemented method for assessing job performance of a ratee comprising an individual worker in an organization in which a person's job performance can be evaluated, the method comprising: in a computer selecting a ratee whose performance is to be appraised, selecting a set of job functions on which the ratee's performance is to be appraised, inputting into a computer-implemented distributional assessment program information relating to the selected ratee, to each selected job function, and to each of a set of aspects of value associated with each job function, the distributional assessment program prompting a user, in a questionnaire-style format, to input data that assigns relative weights to the selected job functions reflecting the relative difference in value each job function can contribute to the organization between an occasion when the job function was performed at its worst effectiveness level and an occasion when the job function was performed at its most nearly perfect level, the distributional assessment program prompting a user, in a questionnaire-style format, to input numerical rating data related to one or more of the aspects of value corresponding to each of the selected job functions associated with the ratee, the program adapted to process the inputted rating data in relation to the inputted weight data to produce a job performance assessment of a ratee that numerically expresses the aggregate effectiveness of the performance distributions achieved on the aspects of value associated with the job functions on which the ratee's performance was appraised, in which the distributional assessment program prompts a user, in a questionnaire-style format, to input numbers expressing a percentage of the ratee's total number of opportunities to perform each of the selected job functions on which it was possible to, or the ratee actually did, achieve each of a set of outcome levels on each of the aspects of value associated with the respective job functions, the program adapted to process the input rating data in combination with the input and pre-established weight data to produce a job performance assessment of the ratee reflecting the proximity of the achieved distribution to a best feasible distribution on each aspect of value associated with each selected job function, on each job function as a whole (comprising the weighted average of scores on the job function's associated aspects of value), on each aspect of value as a whole (comprising the weighted average of scores on the respective aspect of value across all the selected job functions on which it occurs), and on the job as a whole (comprising the weighted average of scores across the job functions or across the aspects of value).