Uneven numbers that tempt you to use the data as the scale. Choose the scale from the range instead.
Practice data: Irregular values such as 11, 47, 116, and uneven gaps between x values.
When the numbers are not tidy
Real results are rarely 10, 20, 30. With values like 11, 47 and 116 it is tempting to write them along the axis. Do not: choose the scale from the range, exactly as before, then plot each value by counting small squares.
The x values may be uneven too (0, 4, 9, 17, 28, 41 s). The scale on the x-axis is still even. The points just are not evenly spaced across it, and that is correct.
Never use the raw data as your scale.
✗ Avoid Raw data on the x-axis: the points will look evenly spaced, which hides the real pattern.✓ Good Even scale: 10 per big square, so 41 is 4 big squares and 1 small square.
Plotting an awkward value
Find the big line just below the value, then count small squares. With 20 per big square, one small square is 4. For 47: the 40 line, then 7 ÷ 4 = 1.75 small squares up. You need to be within half a small square, so put it just under 2 small squares above the 40 line.
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. Oxygen from pondweed
The total volume of oxygen released by pondweed in bright light was recorded every 5 minutes.
Plot a graph of volume of oxygen released against time. Join the points with straight lines using a ruler.[5 marks]
Results Illustrative data
Time / min
Volume of oxygen released / cm³
0
0
5
11
10
23
15
47
20
83
25
116
1 · Axes, labels and scales
Put Time / min (the independent variable) on the x-axis and Volume of oxygen released / cm³ 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?
y: 116 ÷ 10 = 11.6 → round UP to 20 per big square (0 to 200). Do not write 11, 47, 116 on the axis.
