Statistics › Section B · Descriptive statistics › Topic B.3
Percentiles and quartiles
Knowing a value tells you little until you know where it sits among its fellows. Percentiles measure relative standing - and their quartile cousins split data into quarters and hand us a spread measure that outliers barely disturb.
In this topic
- Where do you stand?
- What a percentile means
- Finding the kth percentile
- Worked example: quartiles of bakery sales
- Finding a value's percentile rank
- Worked example: a score's percentile
- Quartiles and the interquartile range
- Worked example: the 1.5 × IQR rule
- Percentiles from grouped tables
- Common mistakes to avoid
- Key takeaways
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