Stage 2 · Lesson 6 of 8
Hypothesis tests and p-values
A starts by assuming there is no effect, the , then asks how surprising your data would be if that were true. The p-value is the probability of seeing a result at least as extreme as yours under the null. If it falls below a threshold chosen in advance, usually 0.05, you reject the null.
Two errors are possible: a , finding an effect that is not there, and a false negative, missing a real one. Power is the chance of detecting a real effect of a given size, and small have little of it.
Common trapreading the p-value as the probability that the null is true, or treating 0.049 and 0.051 as opposite answers rather than nearly the same evidence.
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Resources for this stage
Start with· follow one of these
- VideoFreeStatQuest with Josh Starmer
StatQuest · Beginner
Free: short, clear videos on each concept, from the normal distribution to p-values and power
- CourseFreeKhan Academy Statistics and Probability
Khan Academy · Beginner
Free: the probability, sampling distributions, confidence intervals and significance tests units, with practice