The big picture
Here are the ten ideas, in order.
| Idea | Remember | Example |
|---|---|---|
| One for many | One figure stands in for a set of readings. | 20, 22, 24, 26, 28, 30 |
| The mean | Total shared out equally. A leftover becomes a decimal. | 15 ÷ 4 = 3.75 |
| The median | Sort first. Cross off both ends until one is left. | 7, 9, 11, 12, 15 → 11 |
| An even count | Two are left. The median is halfway between them. | 11 and 12 → 11.5 |
| The mode | Count each value. The tallest pile's label wins. | 5, 6, 6, 7, 6, 8, 7 → 6 |
| An outlier | One far value drags the mean. The median moves less. | 30 → 90: mean 25 → 35 |
| Choosing | The question decides: a share, a middle, or the commonest. | shirt size → mode |
| Dot plot | A dot plot gives each reading one dot on a number line. | 4 dots at 15 → 4 rides |
| The range | The range is the largest reading minus the smallest reading. | 9 − 1 = 8 |
| Double bars | A double-bar graph gives each item two bars, one for each group. | 30 and 25 for mango |
Three recipes can give three different answers. The honest one fits the question asked.