Twelve numbers, one point
The school library kept loan counts for four months and three kinds of book. That is twelve numbers.
The librarian has one minute with the head of English. Which numbers go on the page? Choosing them is the first skill of telling a story with data.
Key words
| Word | What it means | Example |
|---|---|---|
| Data point | One useful figure taken from a dataset. | Fantasy loans rose by 45 |
| Dataset | A collection of related data, often a table. | Four months of loans |
| Materials | The things you make to share a message, such as slides or a report. | A one page summary |
| Requirement | Something the finished materials must do or have. | Fits one page |
| Headline figure | The one number that carries the main point. | Fantasy loans up by 45 |
| Comparison | Two figures set side by side so a difference shows. | September against December |
| Trend | The direction numbers move over time. | Rising each month |
| Exception | A figure that goes against the pattern. | Crime loans fell |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can state what the materials need and pick data points from a dataset that support the story.
Starter: what you already know
Have a go
Starter: what you already know
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Step 1: the requirements of the materials
Before you search the data, write what the materials must do. Who reads them? How long do they have? What one decision or idea must they take away?
These answers tell you how many data points you can use. One page means three or four, not twelve.
Step 2: four kinds of data point
Look for four kinds. The headline figure carries the main point. A comparison shows a difference. A trend shows direction over time. An exception shows what does not fit.
Pick the few that support the story. Leave the rest in the appendix.
Data points from the library loans
| Kind | Data point | Why it helps |
|---|---|---|
| Headline figure | Fantasy loans rose by 45 from September to December | It answers the question in one line |
| Comparison | Fantasy 85 in December against Crime 48 | Shows which genre now leads |
| Trend | Fantasy rose every month | Shows it is not a one month blip |
| Exception | Crime fell from 55 to 48 | Shows the rise is not true for every genre |
The cells students fill in are left blank in this preview.
Try it: find the rise in each genre
select genre,
sum(case when month = 'Dec' then loans end)
- sum(case when month = 'Sep' then loans end) as rise
from loans
group by genre
order by rise desc;
-- Try it: use 'Oct' in place of 'Sep'.
Check: which kind of data point?
Have a go
Check: which kind of data point?
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.