Lesson 9 of 11
The big picture
Show on a big screenEvery question here starts with one careful count.
| Idea | Remember | Example |
|---|---|---|
| The table | Each value once, frequency beside it. | 24 ÷ 20 = mean 1.2 |
| Weighted mean | Each mean times its size, added, divided by the sizes added. | 66, not the halfway 65 |
| Weights | Scores times weights, over the weights added. Same number above 0 on every weight, same grade. | 87.5 at every scale |
| Stacked bar | Pieces as segments. The full height is the total. | 100 quintals, then 200 |
| 100% stacked | Shares only. A count needs a total. | 40%, 25%, 35%, twice |
| Picking charts | A count, a share or a change decides the chart. | A pie needs one whole |
| Two stories | Honest charts can leave different impressions. | Doubled, or unchanged |
| The report | Question, table, average, chart with total, units. | Never "80 what?" |
Open the Class 9 chapter on statistics. Use the five parts of the report as you read.
Before you trust a number, ask which data it came from. Ask what the picture left out.