Stage 2 · Lesson 5 of 8
Confidence intervals
A gives a range for an unknown value, such as the true average order value or , built from your . A 95% interval is roughly the estimate plus or minus 1.96 . It reports the size of an effect and its uncertainty together, which is exactly what a decision-maker needs: "between 4.1% and 5.3%" is more useful than "significant".
Learn to compute intervals for a mean and for a proportion in your language, and to show them on charts.
Common trapsaying there is a 95% chance the true value lies inside this particular interval. The 95% describes the method: if you repeated the study many times, 95% of the intervals built this way would contain the true value.
A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock
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
Practise
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Interactive visuals for probability, distributions, inference and regression: play with each one