Six weeks in three lines
A youth club has six weeks of visitor counts. The leader will not read a table. She wants three lines: how many came, whether it is going up, and how much.
A statistical summary squeezes a table into a few clear facts. This lesson shows which facts, and how to say them.
Key words
| Word | What it means | Example |
|---|---|---|
| Mean | The total of the values divided by how many there are. | The mean of 2, 4 and 6 is 4 |
| Median | The middle value when the values are in order. | The median of 1, 3 and 9 is 3 |
| Trend | The general direction over time: up, down or flat. | Visitors are rising |
| Gain | How much a value has grown from the start to the end. | From 20 to 32 is a gain of 12 |
| Regression | Finding the straight line that best fits the data, to show a trend. | A line through weekly visits |
| Derived data | New data worked out from data you already have. | Visitors per week from daily counts |
| Slope | How steep a line is: how much it rises for each step. | 2 more visitors each week |
| Audience | The people who will read the summary. | The club leader |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can work out key statistics, interpret them, and write a short summary for a reader.
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.
Four outcomes to look for
| Outcome | What it tells you | Example |
|---|---|---|
| Trend | The direction | Visitors are rising |
| Gain | How much it changed | Up by 12 over the six weeks |
| Regression | The best straight line and its slope | About 2.7 more visitors each week |
| Derived data | A new measure worked out | Mean visitors per week |
The cells students fill in are left blank in this preview.
Try it: key statistics in DuckDB
select avg(visitors) as mean, median(visitors) as median,
max(visitors) - min(visitors) as spread,
regr_slope(visitors, week) as slope
from visits;
-- Try it: add min(visitors) and max(visitors) to the list.Try it: the gain in Python
visitors = [20, 24, 23, 29, 33, 32]
gain = visitors[len(visitors) - 1] - visitors[0]
steps = len(visitors) - 1
print("Gain:", gain)
print("Average change each week:", gain / steps)
# Try it: change the last number to 40 and press Run.
Writing it for the reader
Use the right word: say "mean", "median" and "trend", and explain each in a few words for a new reader.
Match the detail to the audience. A leader needs three lines. A colleague may want the method too. Lead with the finding, then give the number.