Measures of Dispersion for Ungrouped Data
Mean
The sum of all values divided by how many there are; the usual average.
| English | Mean |
|---|---|
| Bahasa Melayu | Min |
| 中文 | 平均值 |
How it is used
For 4, 6, 8, 10, 12 the mean is (4+6+8+10+12)/5 = 40/5 = 8. Every later step, such as the variance, is measured as a distance from this mean.
Where it shows up in SPM
In Measures of Dispersion for ungrouped data, and in Measures of Central Tendency. It is almost always the first quantity computed in Paper 2, because variance and standard deviation are built from it.
Don't confuse it with
Open the chapter: Measures of Dispersion for Ungrouped Data →
Frequently asked questions
Is the mean pulled by extreme values?
Yes. Since every value is added in, one very large or very small number shifts the mean toward it.
In a set with a strong outlier the median often describes the centre more fairly, which is why both are sometimes reported.
Do I need the mean before I can find the variance?
Yes. Both variance formulas require the mean: either you subtract it from each value, or you subtract its square from Σx²/N.
So finding the mean accurately is the essential first step before any dispersion calculation.