Data Objectives. The same process can be applied to determine how much simplification is appropriate when describing a geochemical system.

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1 Data Objectives Objectives you identify at the outset of an experiment or scientific study to help determine the nature, amount, and quality of the data you (or someone else) need to collect to answer the questions you are asking with the necessary level of certainty (You can think of data objectives as data collection objectives or data quality objectives, or anything else, as long as you understand their purpose.) The same process can be applied to determine how much simplification is appropriate when describing a geochemical system.

2 To conduct scientifically defensible research You need to establish qualitative and quantitative measures or guidelines to determine whether data is sufficient and sufficiently accurate to draw a conclusion regarding a specific problem or to answer a specific question.

3 Data objectives are used: to determine whether the data collected is accurate and sufficient in type and quantity, and to provide a level of confidence that the conclusions drawn are consistent with the conceptual geochemical model being presented and that the data does not support other conceptual models (If the level of confidence is low, additional data collection is probably necessary or the conclusions should be qualified.)

4 Data objectives will help you: determine when, where, and how many samples or measurements to collect and determine the desired level of confidence in the data needed to justify your interpretation of the data and explain a geochemical system Developing data objectives is really part of the scientific method.

5 You will need to: Summarize the overall objective of the study and the problem for which additional data is needed. Identify the questions that the study will attempt to answer. Identify the type and quality of the data needed to answer the question with the level of assurance that you believe is necessary. Identify the spatial and temporal boundaries for the system that your data is intended to explain.

6 To use the Data Objectives process effectively, you must: Understand the level of confidence that you expect to have in your description or explanation of the geochemical system you are investigating. Consider the consequences of being wrong and how much data do you need to limit the uncertainty in your conclusions to acceptable levels. Design the most resource-effective sampling and analysis plan for generating data that will satisfy the data objectives.

7 Why are data objectives important? Evaluate existing data relative to your data objectives before you begin your study Incorporate usable data into the initial geochemical model Identify gaps in the data set Determine significance of data gaps relative to data objectives Design and implement a sampling plan that will meet your goals

8 Example geochemical questions that data objectives can help you answer: What data are needed to determine chemical inputs to the lake? Would three samples of lake water be sufficient to determine water chemistry in the lake? Would 50 samples be necessary? What chemical analyses should be performed or what chemical parameters should be measured? Is the time-frame over which sampling was conducted sufficient? Should samples be collected at various depths in the lake to adequately characterize the chemical characteristics of the lake water? Can I assume that the effect from biologic organisms will be small and not affect my results enough to change an interpretation?

9 How to Develop Data Objectives 1. Identify and understand the geochemical questions or issues that are to be answered or evaluated. 2. Identify interpretations/conclusions to be made regarding each question or issue. 3. Identify the data you need to answer each question or issue. 4. Define the study boundaries. 5. Develop guidelines to help interpret the data and to recognize when you ve collected enough data. 6. Optimize the design for obtaining data.

10 Developing Data Objectives 1. Identify and understand each question or issue you hope to address. Review prior studies and existing information to gain an understanding of the geochemical system and the issues to be addressed Summarize the questions that require new data to be collected Describe overall study objectives Outline scientific decisions or interpretations that will be made based on the data, and identify the importance of data of each type to making those decisions or interpretations Identify resources available to address the issues

11 2. Identify interpretations/conclusions that will be made with respect to each geochemical question or issue. Identify the types of interpretations/conclusions that will be made using the data Determine degree of certainty that is necessary for each data point

12 3. Identify the data you need to answer each question or issue about the geochemical system that you intend to address or that could affect your interpretation. Determine the information needed to support the interpretations/conclusions you hope to make. Identify aspects of the geochemical model require new data to be collected. Determine the type, quantity, and quality of data needed to develop interpretations/conclusions.

13 4. Define the study boundaries (i.e., specify the spatial and temporal aspects of geochemical system that the data must represent to support the conclusion/interpretation). Define the geographic area or physical boundaries of the investigation. Define the media of interest. Specify the time-frame and range of conditions over which samples will be collected.

14 5. Develop guidelines to help interpret the data and to recognize when the data collected is enough to answer the question with the level of certainty you needed. Consider the conditions that would cause you to choose among alternative interpretations and/or take different directions to interpret the data. Consider the factors that will help you decide when enough data is enough and the additional cost of collecting more data is unlikely to affect your interpretations or conclusions.

15 6. Optimize your design for collecting data. Identify the most resource-effective sampling and analysis design for generating the data that you determined was necessary to collect.

16 Using Multiple Lines of Evidence Because there is inherent uncertainty in any geochemical data set, you can improve the level of confidence in your interpretation if you have several lines of evidence that support your hypothesis. Usually, you will need to consider the different types of data you need before you start collecting any data. Other times, in the process of collecting data a pattern will emerge suggesting additional types of data that might be valuable to collect.

17 Assignment #2 Due Monday, September 15 th Read arsenic in groundwater paper Answer questions on handout sheet

18 Take-home Message #3 The level of confidence you or anyone else can have in your interpretations or conclusions is directly related to the type, location, quantity, and quality of the data that you collect.