(a) one-dimensional linear regression method
The prediction method of linear regression has been described in section III. The method is suitable for cost prediction in the period of little price fluctuations, for price fluctuations, to price caliber conversion, the specific method is as follows.
2-convert the project cost of the preparation year to the cost level of the forecast period
3-establish the regression forecasting model
(ii) time series analysis forecast
1. Calculate the unit square cost of the same type of construction project for each year
A construction company will generally have more than one of the same type of project completed within the same year, and the preparation of the construction project is not possible. The unit square cost of a project may not be the same. In addition, many projects are constructed over a period of years, so if a year is used as a forecasting period, the cost actually reflects more than just the current year's cost level. To address these issues, the following methods can be taken:
(1) usually one year as a forecasting period;
(2) across the year of the project, the actual cost of the year of completion of the cost of information;
(3) in the same year there are a number of similar projects completed, to the average of its cost as the actual cost of that year.
2. Predict the cost of the next year with time-series analysis
After calculating the average annual cost of similar projects in previous years, you can use the time-series Steinbach method of any one of the methods to predict the cost of similar projects in the next year.
The specific calculations are described in the previous section. Here, we suggest using the exponential smoothing method of calculation, because the exponential smoothing method of predicting the value of the results of the value is closer to the actual value than other methods, and is suitable for short- and medium-term forecasting.
(C) exponential curve regression method
For the judgment of the future value of the development of a certain percentage of change year by year, it is necessary to use the exponential curve trend prediction method for prediction. In recent years, due to the rapid development of the economy and the country's price liberalization, the price of goods at a rate of about 10% year-on-year growth, the cost of the construction project also showed a similar trend. Therefore, for this situation, the exponential curve regression method can be taken to predict.
Second, the detailed prediction method
This prediction method, usually on the construction project plan period affects the cost of the various factors to analyze the change, than & gt; according to the most recent completed construction project or will be completed construction project costs (unit area cost or unit volume cost), predict the extent of these factors on the project cost of the relevant items (cost items). Then use the specific gravity method of calculation to predict the unit cost or total cost of the project.
This method, first of all, to calculate the most recent completed or nearly completed similar construction projects (hereinafter referred to as the reference project) of the cost, including the amount of cost items; the second step to analyze the factors affecting the cost, and analyze the predicted preparation for the extent of the impact of factors on the cost of the relevant items; the third step and then by the specific gravity method of calculating the cost of the project predicted to the construction project (hereinafter referred to as the object of the cost of the project).
(B) the structure and construction of the differences in the correction
Due to the special nature of construction products, each project regardless of the structure and architectural design are different, which is to say that the use of the cost of the most recent similar projects as the project's initial projected cost must be necessary to correct. That is, two aspects should be considered: one is the object of the project and the reference project structural differences, the second is the object of the project and the reference project architectural differences.
(C) predict the factors affecting the cost of the project
In the last step of the project cost estimated by the application is almost impossible to be completely consistent with the actual cost of the project, because the process of project construction by the interference of many factors, it is necessary to analyze the cost of the object of the project to influence the factors, and in the next step to determine the degree of impact on the cost of the second step of the estimated cost of the correction; to make it more close to the actual cost, in the management of engineering construction, the cost of the project must be analyzed. Close, play a role in the management of engineering and construction.
In the process of construction, the main factors affecting the cost of the project can be summarized as follows:
1. Material consumption quota increase or decrease, where the material, including fuel, power, etc.
As a result of the use of new materials or material substitution, resulting in a reduction of material consumption or the use of new technologies, new techniques or new equipment, reducing the necessary process losses, and the object of the project and similar projects material level is not the same as that of the project. Object works and similar projects with different material levels at the same time, the difference between the consumption quota and unit price caused by the comprehensive impact.
2. Price increases or decreases
One of the most important factors affecting changes in project costs is due to changes in prices. Some of the main reason for cost overruns is due to the substantial increase in prices, the implementation of fixed-price contracts will often lose money.
3. Labor wage increases
Labor wages (including bonuses, additional wages, etc.) increases inevitably increase the cost of the project, including due to the tight schedule, and increased overtime wages J
4. changes in labor productivity
Workers to enhance the quality of the process or the use of new technology to improve labor productivity, saving the total number of hours of work, thus reducing the cost of construction. The total number of working hours, thus reducing the cost of labor; on the other hand, may be due to the geographical and climatic environment where the project is located, or the quality of the construction team workers with similar projects compared to the low, so that the decline in labor productivity, thus increasing the total number of hours of construction and labor costs.
5. Changes in other direct costs
Other direct costs, including the construction process of the materials occurring in the second handling costs, temporary facilities, production tools and appliances, inspection and testing costs, engineering positioning review costs, engineering point of delivery and site clearance costs, etc., which are different for different projects, the actual cost of its occurrence is different. In predicting the cost, according to the object project and based on the calculation of the difference between the reference project in other direct costs to be corrected.
6. Changes in Indirect Costs
Indirect costs are all the costs incurred by project managers and corporate functions on the construction project. This part of the cost and other direct costs like different projects will be different. If the project scale is different, the number of management personnel on the construction project is also different, the management salary, bonuses, and employee welfare costs are also different.
These factors for the specific project, not necessarily may occur, different projects will not be the same. For example, a period of material prices rise, while another period of material prices will fall. Separate from these two different projects in the same period, the cost will proceed in the opposite direction due to the change in material prices. Therefore, before determining the extent to which cost-affecting factors affect costs, it is important to first analyze which factors are predicted to affect the project.
Predicting the factors affecting the cost of the main qualitative prediction method, that is, to convene the relevant professionals, the use of expert meeting method, the first by the participants to put forward their own views, and then discuss the different views, and finally determine the main factors (see section II).
(D) Predicting the degree of influence of the factors
Predicting the degree of influence of the factors is to predict the changes in the preparation of the factors, and then calculate the results of their impact on the relevant items in the cost.
1. Predict the changes in the factors
The choice of methods for predicting the changes in the factors can be based on the nature of the factors, as well as historical project information, and to adapt to the requirements of timeliness and decision. Generally speaking, the factors applicable forecasting methods are as follows:
(1) changes in material consumption quotas, the application of empirical estimation methods and time series analysis method;
(2) changes in material prices scrupulously, the application of time series analysis, regression analysis and expert survey method;
(3) changes in employee wages, the application of time series analysis and expert survey method;
(3) changes in employee wages, the application of time series analysis and expert survey method;
(3) changes in employee wages, the application of time series analysis and expert survey method;
(4) changes in material prices, the application of time series analysis and expert survey method. p> (4) Labor productivity changes, applying time series analysis and empirical estimation method;
(5) Other direct cost changes, applying empirical estimation and statistical inference method;
(6) Indirect cost changes, applying empirical estimation and regression prediction method.
2. Calculate the degree of influence of each factor on the cost of each factor on the degree of influence of the cost were calculated using the formula
(1) Calculate the cost composition of the project in the cost of the ratio
Calculation methods are as follows: one is to use the ratio of the composition of the cost of the reference project, and the second is to use the ratio of the composition of the cost of the cost of the same type of project in the history of the statistical average.
(2) Calculate the degree of influence of the main factors on the cost
(e) Calculate the forecast cost