Occam's Razor
The simplest explanation that fits the facts is usually the right one — so test it first, not last.
Why PMs should care
When a metric suddenly drops 20% overnight, the cause is almost never 'a complex mix of macro factors and shifting user expectations'. It's usually: someone shipped a bug, a tracking event broke, a landing page was changed by a marketing team nobody told you about, an A/B test started sending traffic to the wrong variant, or a third-party script failed on the most common mobile browser.
The habit that saves you time: check the deployment log before the market research. Check the tracking setup before running a focus group. Check whether the dashboard itself is broken before concluding the product is broken.
The elegant theory is almost always more flattering to the PM's self-image — it makes the story interesting, strategic, worth a leadership conversation. Which is exactly why it should be tested last, not first.
Example in product work
Monday morning: sign-ups collapsed 34% overnight. The leadership Slack channel fills up with theories — 'the Fed announcement on Friday shifted consumer sentiment', 'the new competitor's launch is cannibalising', 'our ad creative is fatigued'.
The PM checks the deployment log: Friday 5pm, a release pushed a change to the mobile sign-up page. Opens it on an actual phone. The 'Continue' button is now below the fold on an iPhone SE.
Total investigation time: 8 minutes. Total time the Slack thread would have spent debating the elegant theories if nobody checked: approximately all day.
Check the simple one first. Always.
What to do when you see it
- When a metric moves sharply, check for the boring explanations before the clever ones.
- Check the deployment log before the market research. Check the tracking first, not the product.
- The elegant theory is usually more flattering to the team — which is exactly why it should be tested last.
- Most surprising dashboard moves are bugs, tracking errors, or someone quietly shipping a change.
Sources & further reading
- Occam's Razor — Farnam StreetShane Parrish's treatment of the principle, its history, and when it breaks down.
- Occam's Razor — BritannicaA scholarly entry on William of Ockham's principle and its role in scientific reasoning.