When making design decisions, you need to evaluate the quality of information and its importance to the project. Two facets of the information that can be evaluated are its trustworthiness and relevance. Trustworthiness include the analyzing the source, audience-level, currency, i.e., the categories in the left column. Relevance relates to the appropriateness of the data to the actual project under consideration, as described in the right hand column.
Once you've found appropriately trustworthy and relevant information for your project, you can feed that information into decision-making structures such as a Pugh Analysis or Weighted Decision Matrix.
When inputting data into those tools, you can see where information gaps exist. For example, you may have operating cost data for one solution but not another.
When identifying information gaps, you need to determine whether that information would make a difference to the final decision or if it is crucial to the decision making (for example, whether it would affect the final decision you make if the entry for that facet changed in your analysis). In the former case, you would probably not bother to locate the information gap, while in the latter, you would want to verify the quality of the information you used in the analysis.