A variety of archaeological Field Evaluation techniques are used by Curatorial Archaeologists in England to assess archaeological remains prior to implementing strategies for their protection through Town and Country Planning or Scheduled Monument Consent procedures. Yet the effectiveness of these techniques and methodologies applied have not previously been quantitatively tested. This innovative research uses Process Modelling to recognise the Decision-making processes within current archaeological Field Evaluation practice. This allows an application of Decision Analysis, a formal theoretical approach to Decision-making, to be used to identify thirteen Decision-making Points (DMPs) and DMP 12b is selected from these as the key point at which the success of Field Evaluation techniques can be tested. Data from a statistically sound Case Study sample of 100 development-led archaeological interventions is recorded using new characterisation and quantitative measurement methodologies. This information is fed into the Process Model of Decision-making Point 12b to provide a measured degree of confidence in the effectiveness of a range of techniques and methodologies. Decision Matrices are produced which show that it is Logically Unsound to rely on Field-walking or Geophysical Survey to identify the type and date of archaeological features. Even Trial Trenching, the most effective technique, can only produce good Performance Scores for the i, dentification of feature types on less than 32% of the Case Study sites. Statistical Analysis of Trenching methodologies shows that an increase to at least a 10% sample size is required for acceptable performance improvements. This research changes the way we look at archaeological Decision-making with the identification of previously unrecognised Conditions of Incomplete Knowledge at DMP 12b. Two original new concepts (Local Locational Factors and Past Landscape Use Patterns) are introduced as tools to assist with these, and their utility for improvements in performance using Predictive Modelling is also explored to provide a body of archaeological research to stimulate the profession and its operators to advance our knowledge of Decision-making into the 2lst Century.