able to answer all relevant questions, and facilitate the process of locating useful evidence for different questions.

“Why” questions relate to the overall question of “Why should we do something about this problem in our situation?” “What” questions ask, “What specifically should we do about this problem?” “How” questions call for examining “How do we implement this information for our situation?”

Locating Evidence

Key Actions: (1) Based on the questions that need to be answered, determine all the types of evidence that could be useful in answering them. (2) Think broadly about the sources of these types of evidence, including the potential for obtaining relevant evidence from other disciplines.

Locating evidence requires a clear concept of the types of information that may be useful for a particular purpose, as well as an awareness of where the information can be found. The framework calls for expanding the evidence paradigm by broadening the perspective on forms of evidence that are potentially relevant and useful, taking full advantage of available research methods for studying population problems, not just those used in medical research. Some forms of available evidence may be underutilized by those who conduct research on obesity prevention because they are unfamiliar to researchers in the biomedical or public health fields.

Locating evidence also requires awareness of and access to appropriate information resources. Databases used by public health researchers and practitioners typically incorporate data from numerous disciplines but may still miss many potentially useful sources. For example, compilations from economics, education, business, and law and information from newspapers, government documents, and reports from community agencies and programs may not be obvious sources of evidence for obesity prevention researchers.

Evaluating Evidence

Key Actions: (1) Recognize the importance of evaluating the quality of the evidence gathered to answer the specified questions. (2) When evaluating evidence, use criteria that are appropriate and established for assessing the quality of that particular type of evidence. (3) In evidence evaluation, pay attention to both the level of certainty (internal validity) and generalizability (external validity) of the evidence.

In the L.E.A.D. framework, the key objectives in evaluating evidence are determining the level of certainty of the causal relationship between an intervention and the observed outcomes (or internal validity) and generalizability to other individuals, settings, contexts, and time frames (or external validity). The level of certainty needed will vary depending on the question. For example, some low-cost interventions with minimal potential for harm may require less certainty than those that are costly or carry the risk of serious harm.

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