Statistics › Section B · Descriptive statistics › Topic B.7
Range, variance, and standard deviation
A centre alone tells half the story. This topic measures how far data travel from their centre - the range, the variance, the standard deviation - and adds the z-score, the ruler that compares values across different data sets.
In this topic
- Centre is not enough
- The range
- The standard deviation
- Computing s, and why n − 1
- Worked example: computing s from a list
- Worked example: s from a frequency table
- Position in SD units
- Worked example: z-scores across two classes
- How much data lies within k SDs
- Choosing centre and spread together
- Common mistakes to avoid
- Key takeaways
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