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P-value is one of the most abused numbers in research. Here is what it actually says — and what it does not. 'Model B is no better than model A.' 'The new prompt does not change user satisfaction.' A low p-value means the boring story would rarely produce data that looks like what you saw.
You see p < 0.05 in papers and headlines constantly. What does it actually mean? Precisely: if the null hypothesis were true, the probability of seeing a result this extreme or more extreme is less than 5 percent.
The null hypothesis is the boring story. 'Model B is no better than model A.' 'The new prompt does not change user satisfaction.' A low p-value means the boring story would rarely produce data that looks like what you saw.
| Phrase heard | What it actually means |
|---|---|
| 'Statistically significant' | P-value below threshold, under one analysis |
| 'Not statistically significant' | Might mean no effect, or might mean not enough data |
| 'Highly significant (p<0.001)' | Less likely by chance under null — but still not proof |
| 'Effect size' | The number that actually matters |
The difference between 'significant' and 'not significant' is not itself statistically significant.
— Gelman and Stern (2006)
The big idea: p-values are one weak piece of evidence, often presented as if they were a verdict. Effect size and replication matter more.
15 questions · take it digitally for instant feedback at tendril.neural-forge.io/learn/quiz/end-builders-statistical-significance
What is the core idea behind "Statistical Significance and P-Values"?
Which term best describes a foundational idea in "Statistical Significance and P-Values"?
A learner studying Statistical Significance and P-Values would need to understand which concept?
Which of these is directly relevant to Statistical Significance and P-Values?
Which of the following is a key point about Statistical Significance and P-Values?
Which of these does NOT belong in a discussion of Statistical Significance and P-Values?
What is the key insight about "What p-value is not" in the context of Statistical Significance and P-Values?
What is the key insight about "Always report effect size" in the context of Statistical Significance and P-Values?
What is the recommended tip about "Build your mental model" in the context of Statistical Significance and P-Values?
Which statement accurately describes an aspect of Statistical Significance and P-Values?
What does working with Statistical Significance and P-Values typically involve?
Which of the following is true about Statistical Significance and P-Values?
Which best describes the scope of "Statistical Significance and P-Values"?
Which section heading best belongs in a lesson about Statistical Significance and P-Values?
Which section heading best belongs in a lesson about Statistical Significance and P-Values?