Time Estimation task

Fig. 105 Alcohol and/or marijuana effect on Brief Interval Time Estimation task (BITE)...

Many project managers find it realistic to estimate time intervals as a range rather than as a precise amount. Another way to deal with the lack of precision in estimating time is to use a commonly accepted formula for that task. Or, if you are working with a mathematical model, you can determine the probability of the work being completed within the estimated time by calculating a standard deviation of the time estimate. 

To use CPM or PERT, the job must first be divided into a number of tasks, and the average time to perform each of the tasks must be estimated. These tasks are called activities. The average time is the usual time it would take to perform the task when doing it the most economical way. To illustrate this, consider a job we have all performed, changing the front tire on an automobile. A list of the activities involved and a time estimate for them is given in Table 13-1. Before looking at that table, the reader should develop his own list and estimate how long each task will take. 

We also wanted to add some way to assess time estimation ability, often included in drug studies. Most previous investigators required the individual to estimate when an arbitrary time interval had elapsed, or to produce a specific time interval, such as one minute. Although popular, we thought these tasks were too imprecise for our purposes. It was often simply a one-trial test, given without prior practice, and useful mainly as a diagnostic tool for psychiatrists and neurologists. 

The project idea has meanwhile gained some shape and it is now the time to add the next dimension to the emerging plan before it becomes too complex. First (conservative) time estimates for the individual tasks can be made. The smallest reasonable time unit for research projects of this magnitude should be a month, less would be unrealistic. Sections and tasks can now be arranged parallel, overlapping or consecutively, according to the time requirements and dependencies. 

Each instructional session ends with a task for which no feedback is given. Sessions are typically 50 min in duration (similar to a class period in high school or college). SPS monitors the time, estimates how far the student will progress through the lessons before the session will end, and terminates the instructional session at an appropriate juncture, usually at the conclusion of a paired set of an instructional lesson and its related exercises. Before the student leaves the workstation, he or she is asked to... 

In the 1993 Defense Appropriations Act, Congress directed the Army to report the locations, types, and quantities of non-stockpile chemical materiel to report the methods to be used for its destruction to provide cost and time estimates and to assess transportation options. A survey and analysis report provided an overview of the task facing the Army (U.S. Army, 1993, updated in draft form in 1996). 

Develop time estimates and a preliminary schedule of tasks. 

Develop Time Estimates and Preliminary Schedule of Tasks... 

The next step is to develop time estimates for each task. The time estimates take two forms ... 

The effort and duration estimates should be developed from the bottom up, preferably by the persons responsible for their execution, in contrast to the top-down, high-level estimates prepared during the project definition phase. They should take into account past experiences with similar, standard processes, to the extent possible. As predictions, the estimates should be equally Ukely to be above or below the actual results rather than represent the minimum or maximum time. Figure 4 provides an example of task time estimates. 

Wj is the adjustment weight for the kth piece of evidence, i(x>) is the subjective evaluation of the kth piece of evidence, and R is the reference point ageiinst which the fcth piece of evidence is compared. In evaluation tasks, R = 0. This corresponds to the case where evidence is either for or against a hypothesis. For estimation tasks, R i= 0. The different values of R result in an additive model for evaluation tasks and an averaging model for estimation tasks. Also, if the quantity, s(x,) - R, is evaluated for several pieces of evidence at a time, the model predicts primacy effects. If single pieces of evidence are individually evaluated in a step-by-step sequence, recency effects become more likely. 

Note that this is the standard FIR form as discussed in Chapter 3, but the output is an estimate of the next sample in time. The task of linear prediction is to select the vector of predictor coefficients ... 

This chapter will focus on practicable methods to perform both the model specification and model estimation tasks for systems/models that are static or dynamic and linear or nonlinear. Only the stationary case win be detailed here, although the potential use of nonstationary methods will be also discussed briefly when appropriate. In aU cases, the models will take deterministic form, except for the presence of additive error terms (model residuals). Note that stochastic experimental inputs (and, consequently, outputs) may stiU be used in connection with deterministic models. The cases of multiple inputs and/or outputs (including multidimensional inputs/outputs, e.g., spatio-temporal) as well as lumped or distributed systems, will not be addressed in the interest of brevity. It will also be assumed that the data (single input and single output) are in the form of evenly sampled time-series, and the employed models are in discretetime form (e.g., difference equations instead of differential equations, discrete summations instead of integrals). 

Task-time line analysis Temporal onset, duration, and concurrences Task-load estimates Task complexity... 

Keystroke-level performance model Models the performance (i.e., time) estimated for executing each of six defined actions, from which overall estimated task completion times can be computed Performance is modeled by assigning time values to each of six modeled actions... 

Skills, rules, and knowledge model Models human information processing in terms of three levels of behavioral control skill based, rule based, and knowledge based Models the processes and requirements for each level of behavior Can be used with quantitative models of human performance to estimate task time and errors... 

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