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Answer: Acknowledge uncertainty. Tell readers what you know, what you don't know, and what process you are using to get answers.

CDC Clear Communication Index (item 11)

• Explain what subject matter experts and agency spokespersons know and don't know about the topic.
• Be open about uncertainty in data, findings, recommendations, guidance, and action steps.
• What we know today may not be complete or fully accurate, and acknowledging that introduces the idea that findings and recommendations may change over time.

CDC CERC: Psychology of a Crisis

• Many communicators have been taught to sound confident even when they are uncertain; overconfidence can backfire.
• Acknowledge uncertainty and share the process you are using to get more information about the evolving situation.
• Promise only what you can be sure you will do, not an outcome outside your control.

See also

• plain-one-main-message
• plain-explain-why-and-how

Claims

• id: C1 claim: CCI asks whether material explains what is known and not known. source: S1 evidence: "know and don’t know about the topic?"

• id: C2 claim: CCI: acknowledge uncertainty. source: S1 evidence: "Acknowledge uncertainty about data, findings, recommendations, guidance and action steps."

• id: C3 claim: CERC: tell what you know, what you do not, and the process. source: S2 evidence: "What process you are using to get answers."

• id: C4 claim: CERC: overconfidence can backfire. source: S2 evidence: "there is a potential for overconfidence, which can backfire."

Sources

• [S1] CDC Clear Communication Index: User Guide. Centers for Disease Control and Prevention (CDC). https://www.cdc.gov/ccindex/pdf/clear-communication-user-guide.pdf . License: US government work, public domain. Accessed 2026-11-09.

• [S2] CERC: Psychology of a Crisis. Centers for Disease Control and Prevention (CDC). https://www.cdc.gov/cerc/media/pdfs/CERC_Psychology_of_a_Crisis.pdf . License: US government work, public domain. Accessed 2026-11-09.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Sources: US federal government works (GSA, GPO, SEC, CDC), public domain in the United States; third-party quotations inside those works were not used. Text was condensed and changed from the originals.

@misc{iil_note_1wp26bqv,
  author = {{iinventedlight}},
  title = {{Say what is known, what is not, and how you will find out}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-09},
  url = {https://iinventedlight.com/library/notes/plain-state-known-unknown/},
  note = {Permanent ID iil:note:1wp26bqv. License: CC-BY-4.0.},
}

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