DQOs are qualitative and quantitative statements, developed in the first six steps of the
DQO Process (Figure 3-1), that define the purpose for the data collection effort, clarify the kind of data
needed, and specify the limits on decision errors needed for the study. These outputs are used in the
final DQO step to develop a sampling design that meets the performance criteria and other design
constraints. The DQO Process helps investigators ensure that the data collected are of the right type,
quantity, and quality needed to answer research questions or support environmental decisions, and
ensures that valuable resources are spent on collecting only those data necessary to support defensible
decisions.
The DQO Process is a systematic planning approach for data collection that is based on the
scientific method and uses a seven-step process. Although the DQO Process is typically described in
linear terms, it is really a flexible process that relies on iteration and modification as the planning team
works through each step, thus allowing early steps to be revised in light of information developed from
subsequent steps.
The Steps of the DQO Process
Step 1: State the Problem. This step
defines the problem clearly, identifies the primary
decision maker and planning team members, and
determines the available budget, personnel, and
schedule deadlines.
Step 2: Identify the Decision. The key
activities are to develop an appropriate decision
statement: identify the principal study question,
define alternative actions that could result from
resolving the principal study question, link the
principal study question to possible actions, and
organize multiple decisions.
Step 3: Identify the Inputs to the
Decision. These activities include identifying the
type and sources of information needed to resolve
the decision statement, identifying information
needed to establish the action level, and confirming
that suitable methods exist.
Step 4: Define the Boundaries of the
Study. This step specifies the characteristics that
Step 1. State the Problem
Define the problem; identify the planning team;
examine budget, schedule.
Step 2. Identify the Decision
State decision; identify study question; define
alternative actions.
Step 3. Identify the Inputs to the Decision
Identify information needed for the decision (information
sources, basis for Action Level, sampling/analysis method).
Step 4. Define the Boundaries of the Study
Specify sample characteristics; define
spatial/temporal limits, units of decision making.
Step 5. Develop a Decision Rule
Define statistical parameter (mean, median); specify
Action Level; develop logic for action.
Step 6. Specify Tolerable Limits on Decision Errors
Set acceptable limits for decision errors relative to
consequences (health effects, costs).
Step 7. Optimize the Design for Obtaining Data
Select resource-effective sampling and analysis plan that
meets the performance criteria.
Figure 3-1. The DQO Process
Final
EPA QA/G-5S
18 December 2002