Methodology

How we research

Every claim that affects someone's safety, health or money links to its source. Here's how we choose those sources and keep guides current.

Our evidence ranking

When sources disagree, we follow the stronger evidence. From strongest to weakest:

1. Systematic reviews and meta-analyses, such as Cochrane reviews and those indexed in PubMed.
2. Peer-reviewed primary studies, including randomized trials and field research.
3. Official guidance from agencies such as FEMA, CDC, NOAA and the National Weather Service, USDA, DOE, EPA, the American Red Cross, GOV.UK and national civil defence agencies.
4. University extension services and national laboratories, such as the National Center for Home Food Preservation and NREL.
5. Expert practice, used only where nothing stronger exists, and labeled as such.

For emergency instructions (what to do in a tornado, a flood or a radiation emergency) we follow official guidance exactly, because that's what emergency services will expect you to do.

Quick cards and full guides

Each guide opens with a quick card: what to do before, during and after, and what to have on hand. The full guide below it explains the reasons. Both are written from the same source list, so they never disagree.

Review dates

Each guide shows the date its sources were last checked and the status of its expert review. We recheck every guide against its sources at least once a year, and sooner when an agency updates its guidance.

Forecasts are labeled

Articles in our Future section look ahead. They're clearly labeled as forecasts and kept separate from safety guidance.

Shopping

Products in our shop are chosen to match items on official checklists. Product listings never change what a guide recommends.