Estimating Highway Preconstruction Services Costs - Volume 1: Guidebook (2016)

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62 Adjusted R-Squared (Adjusted R2) Also called adjusted R2. It is a modification of the R-squared value based on the number of independent variables used in the model. “The adjusted R2 is always less than or equal to the original R2, and the discrepancy gets larger as the number of independent variables increases” (Allison 1999). Advertise “To make a public announcement of the intention to purchase goods, services, or construction with the intention of increasing the response and enlarging the competition. The announcement must conform to the legal requirements imposed by established laws, rules, policies, and procedures to inform the public” (Shields 1998). Artificial Neural Network “Artificial neural networks are capable of learning complex relationships in data. By mimicking the functions of the brain, they can discern patterns in data, and then extrapolate predictions when given new data” (Palisade Corporation 2010). Bottom-Up Estimates “Detailed estimates of work packages usually made by those who are most familiar with the task (also called micro estimates)” (Larson and Gray 2011). Construction Services All activities performed after contract award intended to construct the project as defined in the project design and contract documents. Data Cleaning “Data cleaning, also called data cleansing or scrubbing, deals with detecting and removing errors and inconsistencies from data in order to improve the quality of the data” (Rahm and Do 2000). Data Collection “Data collection is the process of gathering and measuring information on variables of interest, in an established systematic fashion that enables one to answer stated research questions, test hypotheses, and evaluate outcomes” (Northern Illinois University, n.d.). Decision Tree “A decision tree can be used as a model for a sequential decision problems under uncertainty. A decision tree describes graphically the decisions to be made, the events that may occur, and the outcomes associated with combi- nations of decisions and events. Probabilities are assigned to the events, and values are determined for each outcome. A major goal of the analysis is to determine the best decisions” (TreePlan Software, Inc., 2016). Dependent Variable “. . . the variable whose values are supposed to be explained by changes in the other variables (the independent or explanatory variables)” (University of California – Berkeley 2016). A P P E N D I X A Glossary of Preconstruction Services Cost-Estimating Terms

Glossary of Preconstruction Services Cost-Estimating Terms 63 Final Design “. . . any design activities following preliminary design and expressly includes the preparation of final construction plans and detailed specifications for the performance of construction work” (23 CFR 636.103 2002). Independent Variable “The independent variable predicts change in another variable [dependent variable]” (World of Sociology 2001). Line-Based Projects These are projects that can be represented by a line diagram. They include pavement works, grading, landscaping, and right-of-way, which can be geo- graphically referenced linearly in a geographical information system (GIS). These types of projects are easier to be identified using the exact coordinates and stations in collecting data as an integral part of GIS that will help in the design and management of projects. Multiple Regression “. . . statistical method for studying the relationship between a single dependent variable and one or more independent variables” (Allison 2009). Planning “It involves the choice of technology, the definition of work tasks, the estimation of the required resources and durations for individual tasks, and the identification of any interactions among the different work tasks” (Hendrickson 2000). Point-Based Project These types of projects typically incorporate bridges, culverts, and build- ings that can be represented by a single point with respect to their locations on GIS. Polygon/ Multi-line Project These type of projects cannot be represented by a single point or line. The shape and design of these projects can only be represented by a combination of lines or a set of polygon-type geometry when being represented geographically in an information system. Preconstruction Services Costs (for estimating) All expenses incurred by the agency after the project identification number assignment and the award of the contract. Preliminary Design It “defines the general project location and design concepts. It includes, but is not limited to, preliminary engineering and other activities and analyses, such as environmental assessments, topographic surveys, metes and bounds surveys, geotechnical investigations, hydrologic analysis, hydraulic analysis, utility engineering, traffic studies, financial plans, revenue estimates, hazard- ous materials assessments, general estimates of the types and quantities of materials, and other work needed to establish parameters for the final design” (23 CFR 636.103 2002). R-Squared The “. . . portion of the variation in the responses y [estimates] that is explained by the model” (Ott and Longnecker 2010). Top-Down Estimates “Rough estimates that use surrogates to estimate project time and cost (also called macro estimates)” (Larson and Gray 2011). Training Data Set Data set used to build the model (Palisade Corporation 2010). Validation Data Set Data set used to test the accuracy of the model (Palisade Corporation 2010).