【国外标准】 Standard Guide for Schedule Performance Index, Schedule Beta (βs)

5.1 The schedule beta (βs) approach produces informational elements: Overall (or composite) schedule beta (βs), schedule beta upside (βs+), and schedule beta downside (βs–)—representing the quantitative components, and the qualitative insight (“early warning”) into the propensity for directional schedule performance for individual schedule participants.5.1.1 The quantitative component of schedule beta (βs) (inclusive of the upside and downside subvariants) is an index value that depicts schedule participant’s magnitude and direction of movement as compared to the overall project at an assigned value of 1.0, for example, a βs = +2.5 connotes performance of a schedule participant that moves in the same direction as the collection of completed projects at a rate of 2.5 units (schedule days) for each single unit (schedule day) experienced at the overall project level.5.1.2 The qualitative component of schedule beta (βs) (inclusive of the upside and downside subvariants) provides insight as a cautionary and predictive signal depicting the ability for an individual schedule participant to perform in-keeping with the initially-established as-planned schedule duration(s).5.2 Schedule beta (βs) also depicts the overall status or health (performing well or not) of a market sector, location and/or trade. Consistent larger schedule beta (βs) values are indicative of external elements (risks) impacting all participants sharing common attribute(s) (that is, trade, location, market sector, etc.).5.3 Schedule beta (βs) measures current schedule participant performance. As a rolling value (for example, calculated for projects completed during the two most recently completed full calendar years), it depicts the schedule performance ability of the schedule participant. See Note 1.NOTE 1: Schedule Data Source and Usage—Schedule beta (βs) (inclusive of the upside and downside subvariants) utilizes schedule data from any schedule calculation method that depicts individual activity duration versus overall project duration and is updated on a regular basis. Data are used for calculation, comparison, and/or contrasting purposes. They are not created under this guide. Schedule beta (βs) uses four data points from the external scheduling method: as-planned and as-built durations for both individual activity and the overall construction project in its calculation – see Section 3 for definitions.5.3.1 Improving Values—Schedule beta (βs), schedule beta upside (βs+), and schedule beta downside (βs–) are characterized as improving when their value decreases in magnitude (that is, βs = +2.5 becomes βs = +1.75 and βs = –1.25 becomes βs = –3.0).5.3.2 Deteriorating Values—Schedule beta (βs), schedule beta upside (βs+), and schedule beta downside (βs–) are characterized as deteriorating when their value increases in magnitude (that is, βs = +0.5 becomes βs = +1. 5 and βs = –2.25 becomes βs = –1.0).5.4 Schedule beta (βs) (inclusive of the upside and downside subvariants) is capable of being calculated any time a project reaches completion and no further activity (no additional days) are recorded within an overall project schedule.5.4.1 Any schedule participant having completed their work in at least two (2) distinct (mutually exclusive) completed projects may calculate the full array of schedule beta values—schedule beta (βs), schedule beta upside (βs+), and schedule beta downside (βs–).1.1 This guide covers schedule beta (βs), which measures construction project participant schedule performance versus that of the overall completed project and is based on beta (β) from financial portfolio theory for measuring the correlation between individual stock performance and that of the overall stock market.2 By correlating the delta of actual activity performance (“as-built”) minus that originally scheduled (“as-planned”) to the delta of as-built minus as-planned for the overall completed project for a participant’s collection of projects over a specified period of time, a schedule performance index is established in a similar manner as the aforementioned beta (β) of an individual stock.1.2 Schedule beta (βs) measures, as a unitless index value, schedule participant (“subcontractor’s”) performance—ahead or behind—as-planned duration as correlated to its respective overall project’s schedule performance.1.3 Schedule beta (βs) is measured with input from at least two (2) independent (mutually exclusive) projects that have reached completion, within the defined period of observation.1.4 Schedule beta (βs) is measured across a standard predetermined period of time, in similar fashion to that of the insurance industry’s experience modification rate’s (EMR) most recent two (2) complete calendar years within the past thirty-six (36) months.1.5 Schedule beta (βs) evaluates schedule participant’s (“subcontractor’s”) most recent performance, not its complete history, such that is it indicative of current performance and contemporary influences—market, geographic, industry trade, etc.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.