Sancho PM· Practice · 4 min read
The Enchanted Helmet
When Data Blinds Instead of Guides
Don Quixote saw a magical helmet. It was a barber's basin. PMs see insights in dashboards that aren't there. Sancho knew the difference.
The Golden Helmet
At one point in his adventures, Don Quixote spots a man on a donkey wearing what the knight insists is the legendary Helmet of Mambrino—a magical golden helmet that makes its wearer invincible.
Sancho squints. “That’s… a barber’s basin, sir.”
Quixote doesn’t care. He attacks, claims the “helmet,” and wears it proudly for chapters.
It was still a basin.
In Product Management
We do this with data all the time.
Your data is a barber’s basin if the number everyone celebrates doesn’t connect to the outcome that actually matters. Page views are climbing—great. But conversion is flat, retention is dropping, and nobody’s buying. The number goes up, so it must be good. It isn’t. You’re wearing a basin and calling it gold.
Your data is a barber’s basin if you’ve confused the arrow of causation. “Users who complete onboarding retain at 50% higher rates—let’s force everyone through onboarding!” But engaged users complete onboarding because they’re already engaged, not the other way around. It’s the same energy as shipping an A/B test that “won” at 51% confidence—statistical significance ignored for the thrill of a decision.
Your data is a barber’s basin if your dashboard feels like insight but changes nothing. You stare at the charts, convinced they’re telling you something profound. Usually they’re showing you numbers you already knew, packaged in prettier colors. If no decision would change based on what’s on the screen, you’re not analyzing—you’re decorating.
We see magical helmets everywhere. They’re mostly basins.
The Sancho Approach
Sancho didn’t see magical armor. He saw a bowl. Here’s his approach to data:
1. Call the Basin a Basin
Before celebrating a metric, Sancho would ask: what is this number actually measuring? If MAU doubled overnight but DAU stayed flat, would you actually be winning? Strip away the label and look at the thing itself. A number that goes up isn’t automatically good news—it depends entirely on what’s being counted and why.
2. Seek the Metric That Hurts
Quixote avoided information that challenged his fantasy. Sancho looked for truth, even when it was uncomfortable. Find the metric your team doesn’t want to talk about—that’s probably the one that matters. Data is evidence, not a verdict. No dashboard should make a decision for you; it shows what happened, and your judgment says what to do about it.
3. Get Comfortable Saying “I Don’t Know”
Quixote was certain of everything. Sancho was comfortable with uncertainty. “We don’t have enough data to know” is a valid answer—often the most honest one. Better to sit with ambiguity than to pretend a basin is a helmet because you needed a decision by Friday.
Dangerous Data Patterns
If any of these sound familiar, you might be wearing a basin:
- Cherry-picking time ranges to show improvement
- Celebrating inputs (signups) instead of outcomes (retained users)
- Ignoring segments that don’t fit the narrative
- Confusing correlation with causation
- Waiting for perfect data while reality happens
The Metric That Matters
Before acting on any dashboard or metric, run through this checklist:
- Identify the real measurement. Strip away the label and ask what this number actually tracks. If you can’t explain it in one sentence, you don’t understand it yet.
- Find the blind spot. Every metric hides something. Name what this one doesn’t tell you—and decide whether that gap changes the decision.
- Require a decision trigger. If this metric changed dramatically, what would you do differently? If the answer is “nothing,” stop tracking it.
If you can’t clear these three checks, you might be staring at a barber’s basin.
Pragmatic, Not Anti-Data
This isn’t about ignoring data. It’s about seeing clearly.
Data is useful when you know what it is. Dangerous when you pretend it’s something magical.
Sancho would look at the basin and use it—for washing, not for battle. Know your basins. Use them appropriately.
Start here
Run your current dashboard through the checklist above. The Success Metrics template can help you separate the helmets from the basins—and build a measurement practice that actually informs decisions.
