【導(dǎo)讀】原則，同樣好估計(jì)做法。估計(jì)值必須是現(xiàn)實(shí)的準(zhǔn)確反映。估計(jì)應(yīng)該只顯示一個(gè)細(xì)。節(jié)的水平是相關(guān)的決定。完整性要求的項(xiàng)目，它包括所有尚未加入任何額外費(fèi)用。文件必須是一個(gè)可以理解的，檢查，核實(shí)，并糾正形式。必須注意的直接和間接。費(fèi)用和可變成本和固定成本之間的區(qū)別。應(yīng)急突發(fā)事件可能或覆蓋。查明事件的預(yù)期值和預(yù)期的事件會(huì)發(fā)生，無法事先確定。為了估計(jì)是制作的材料，時(shí)間，數(shù)量或成本近似的語句來執(zhí)行施工。稱為數(shù)量的報(bào)表估計(jì)，其目的是為施工決策提供信息。施工價(jià)格，建立和控制支付合同金額按項(xiàng)目管理的實(shí)際數(shù)量。財(cái)務(wù)報(bào)表必須符合公認(rèn)的會(huì)計(jì)。估計(jì)文學(xué)不提供類似的普遍接受的估算方法估算抵銷可以判斷原則。雙方還要求，可從項(xiàng)。目到項(xiàng)目或重復(fù)期間內(nèi)的標(biāo)準(zhǔn)做法。的文獻(xiàn)對(duì)估算的做法。這使得特別是在教學(xué)評(píng)估無效的，無論是在學(xué)。到此可延遲，這將發(fā)生之前，該項(xiàng)目已完成的增減費(fèi)用。應(yīng)該出現(xiàn)尷尬將它作為解決糾紛的證據(jù)。選剛性，演示格式不適合于估算過程。

　　

【正文】 direct project cost. The owner will have additional direct project cost for architect/engineer and its own direct expenses for supervision, furnishing, startup, etc. Thus one party’s indirect costs and markups bee another party’s direct cost. In fact, if the owner were building a production plant, all the project’s direct costs and indirect costs are transmitted to customers as their direct costs of purchasing products manufactured at the plant. Variable and Fixed Costs Costs can be classified by whether they change as the volume produced changes. Volume or quantity of construction activity is measured in many ways, such as linear feet (linear meters), square feet (square meters), or cubic yards (cubic meters) produced, hours worked, units installed, and months rented. If a cost changes in proportion to a change in volume or quantity, it is variable. If a cost remains unchanged in total despite wide fluctuations in volume or quantity, it is fixed. Most activities are a mixture of variable and fixed costs. An example is a jobsite shop to fabricate spools of pipe, which consists of four welding bays, two cutting bays, a storage area, and an overhead crane. The cost of setting up the shop is a fixed cost of fabrication, because once it is set up, its cost will not change if half as much or twice as much pipe is fabricated as was expected. However, the hours of wages paid to pipefitters depends on the number of spools fabricated, as does the length of rental of welding machines, the fee of the weld inspector, and quantity of pipe. These are all variable costs of pipe fabrication. Most of general and administrative costs, such as main office rent, insurance, taxes, and depreciation。 salaries of main office personnel。 and ownership costs of equipment。 can be considered fixed for a given time period. They are often called period costs, because they occur or expire with time. Though considered fixed over a given time period, they may change considerably from one period of time to another as the level of business changes or as equipment or real estate is bought or sold. Many project overhead costs are fixed, particularly costs of installing jobsite services. Examples of fixed costs for a broad range of project quantities produced are installation of electric and phone service to the job site and installation of shops, hoist, parking, and warehouse facilities. Project insurance and building permit are variable costs because they vary directly with cost of construction. Project supervision, security, and rental for crane and jobsite offices are project period costs. They vary with length of project and are therefore considered variable costs. The difference between variable and fixed costs is particularly important in determining relevant costs for changes in contract quantities. The two mon types of petition are lump sum bids that give the owner fixed prices and unit price bids that give the owner sets of variable costs. However, neither accurately represents a contractor’s costs, which are a mixture of variable and fixed costs. Each type of contract allows adjustment for the differences between the contract representation and the real cost picture. Though the lump sum contract contains no variable costs, its general conditions allow an owner to adjust quantities by change orders and make provision for changes in contract sum to recognize changes in quantities. Unit price contracts are designed to be more easily adjusted. But because the unit prices represent a mixture of fixed and variable costs, a change in quantity affects contract amount by more than the variable cost. Large quantity changes can cause major inequities for contractor or owner, and unit price contracts usually contain clauses allowing renegotiation of unit prices if there are major changes in quantities. 3 Contingency An estimate is a prediction—an approximation—that provides information for decisions and is a surrogate or substitute for actual measurement that is not economical or possible. It is considered accurate if it is sufficiently close to actual performance that decisions based on the estimate are the same as decisions based on actual performance, were actual performance available. Though the guiding concept of an estimator is accuracy, by its nature an estimate is uncertain. An estimator must live with uncertainty, though it is not his friend. In fact an estimator must not only live with uncertainty, but he must estimate and control uncertainty, because the uncertainty contained in an estimate is as important information as the estimated value itself. A contingency is a possible or unforeseen occurrence. In estimating, the word contingency is used for two types of estimates. The first is the expected value of a possible identified event. For example, if there is a 20% chance a contractor may require two dozers instead of one, it may include a cost of 20% (or more) of the cost of the second dozer as a contingency. The second type of contingency is the possible cost of unforeseen events: events that cannot be identified because the engineer does not know what can happen. This second type is a true contingency and the one that needs close attention, because it is a margin for error. The most worrisome thing in engineering (and probably in every profession) is the occurrence of the unanticipated. The possibility of unanticipated events flies in the face of the knowledge that is the cornerstone of professional practice and control. The unanticipated may be of such a magnitude and consequence that it overwhelms ones carefully considered decisions and actions, and it controls the oute. The worst of it, however, is not to know when one does not know, not to know when to expect error, and not to provide for the occurrence of expected error. An estimator is strongly in