--- title: Family-Wise Error Rate - Definition & Examples | RGM® Glossary url: https://realgrowthmatters.com/glossary/family-wise-error-rate/ updated: 2026-06-10 source_html: https://realgrowthmatters.com/glossary/family-wise-error-rate/ --- Growth Glossary — Definition SHT FAMILY-WISE-ER # Family-Wise Error Rate Probability of any false positive across multiple tests. A working definition from the RGM marketing glossary. Probability of any false positive across multiple tests. Term : Family-Wise Error Rate Field : Statistics & Analytics Category : Statistics & Analytics ## What it means Look at it this way.Treat Family-Wise Error Rate as an analytical concept with a clear scope. Two people using the term should mean the same thing. Probability of any false positive across multiple tests. Family-Wise Error Rate sits in Statistics & Analytics; it is an analytical concept. Define it once and the reporting holds together. ## How operators apply it Start here.There is no single setting for Family-Wise Error Rate. It bends to the audience, the channels, and the wider plan. Family-Wise Error Rate is not a switch you flip. It names a moving idea, and the way it plays out shifts with the setup. A lean team running one paid channel applies Family-Wise Error Rate differently than a brand running ten. Use Family-Wise Error Rate loosely and teams pull apart; pin it down and the math lines up. One rule always holds. Settle the scope of Family-Wise Error Rate up front, then build the plan. Get it backwards and Family-Wise Error Rate becomes a word everyone uses and no one shares. Read that twice. ## When to reach for it Hold that thought.Use Family-Wise Error Rate when it changes a choice. If it is not driving a decision, it is vocabulary, not leverage. Family-Wise Error Rate matters at the point of a decision. In statistics & analytics, three moments come up again and again. Outside them, Family-Wise Error Rate is reference material. 1. **Setting budget.** Family-Wise Error Rate signals which line earns the marginal spend. 2. **Choosing a metric.** Family-Wise Error Rate reveals if the metric measures real impact. 3. **Comparing options.** Family-Wise Error Rate adjusts a compare so the gap is honest. ## An example with real numbers Hold that thought.Below, Family-Wise Error Rate is put inside a Duolingo setting -- real trade-offs, a clear baseline, and a figure to test it. Look at Duolingo. In a power-analysis discipline, Family-Wise Error Rate drove the decision rather than sitting in a footnote. A baseline came first, then a single agreed meaning of Family-Wise Error Rate, then the read: fewer false wins shipped. The numbers behind Family-Wise Error Rate -- illustrative only, RGM analysis | Stage | What the team did | Why it mattered | | Baseline | Took a before reading on Family-Wise Error Rate. | A reference to judge against. | | Define | Fixed one meaning of Family-Wise Error Rate for the test. | No room for scope drift. | | Act | A power-analysis discipline — one variable. | Cause and effect, isolated. | | Result | Fewer false wins shipped | A call backed by the read. | These Family-Wise Error Rate numbers are illustrative -- RGM analysis. The structure travels; the specific figures do not. ## Pitfalls in practice Look at it this way.Four failure modes recur with Family-Wise Error Rate. Name them and they are easy to design around. - **No segments.** Treating Family-Wise Error Rate as one number for all. Break it out before you trust it. - **No anchor.** Quoting Family-Wise Error Rate without a starting point. Always pair it with a baseline. - **Wrong target.** Treating Family-Wise Error Rate as the goal. The goal is the outcome it predicts. - **Raw benchmarks.** Stacking Family-Wise Error Rate against rivals blind. Normalize for margin, pricing, and sales cycle. ## Frequently asked questions How is Family-Wise Error Rate defined? Probability of any false positive across multiple tests. In short, fix that meaning before any tactic is debated. Why does Family-Wise Error Rate matter for marketers? Family-Wise Error Rate matters because vague vocabulary breaks strategy. A precise, shared definition keeps a team aligned. How is Family-Wise Error Rate used in practice? Family-Wise Error Rate informs a decision -- most often a budget, a metric choice, or a comparison. The Duolingo example above shows the pattern. Where do teams slip up on Family-Wise Error Rate? Chasing Family-Wise Error Rate as a goal and benchmarking it raw. Both bury the real trade-off underneath. How is Family-Wise Error Rate defined? : Probability of any false positive across multiple tests. In short, fix that meaning before any tactic is debated. Why does Family-Wise Error Rate matter for marketers? : Family-Wise Error Rate matters because vague vocabulary breaks strategy. A precise, shared definition keeps a team aligned. How is Family-Wise Error Rate used in practice? : Family-Wise Error Rate informs a decision -- most often a budget, a metric choice, or a comparison. The Duolingo example above shows the pattern. ### Related guides ### Related terms