Round numbers, but different ranges: practise picking 5, 10, 20, 50 or 100 per big square.
Practice data: Round values (10, 20, 30 …) with ranges that need different steps.
Same method, different sizes
Round data makes plotting easy, but you still have to choose the step. Data up to 60 on 8 big squares needs 10 per big square; data up to 180 on 10 big squares needs 20; data up to 900 needs 100.
Before you plot, work out what one small square is worth: the step ÷ 5. With 20 per big square, one small square is 4.
Range ÷ big squares → round UP to 1, 2 or 5 × 10ⁿ → check more than half the grid is used.
The SLAPUK mark scheme
SLAPUK
Out of 5 (S L A P U). Out of 6 (S L A P U K) when there is more than one data set on the graph.
S
Scale
Even steps of 1, 2, 5 or 10 (×10ⁿ), and the data uses more than half the grid each way. Never use the raw data as your scale.
L
Line
Join the points with straight lines using a ruler, point to point. Best fit only when the question asks.
A
Axes
What you changed goes on x, what you measured goes on y. Copy the table headings as the labels.
P
Plots
Every point within half a small square, drawn as a small × or ⊙.
U
Units
Units after a slash or in brackets: "Time / min" or "Temperature (°C)".
K
Key
Only for two or more data sets: a key that says which line is which.
Practice graphs
1. Seeds and temperature
Groups of 100 cress seeds were kept at different temperatures and the percentage that germinated was recorded.
Plot a graph of percentage of seeds germinated against temperature. Join the points with straight lines using a ruler.[5 marks]
Results Illustrative data
Temperature / °C
Percentage of seeds germinated / %
10
15
20
40
30
85
40
70
50
10
1 · Axes, labels and scales
Put Temperature / °C (the independent variable) on the x-axis and Percentage of seeds germinated / % on the y-axis. This grid is 8 big squares across and 10 up; each big square has 5 × 5 small squares.
Set your scales, then tap the grid to plot each point.
Keyboard and screen-reader entry
Values are placed using the scale you set, so a wrong scale still gives a wrong graph – just like on paper.
Stuck on the scale?
Range ÷ big squares, then round UP to 1, 2 or 5 (× 10, 100 …). Check the data uses more than half the grid.
