2.1.4 Labelling Graphs & Tables

• There are specific conventions for labelling physical quantities in columns of data in tables and on graph axes

Table Conventions

• When labelling table headings, the symbol is presented first, then a forward slash and the unit
  • e.g. Current with unit Amps – I / A

• The general convention for tables:
  • The independent variable goes in the column on the left
  • The dependent variable goes in the column on the right

• Sometimes, powers of tens are also included with the unit, such as t / × 10² s
  • This means the column of data has been divided by 100 to save repeating lots of zeros in the table
  • If the values of t in the table or axes on the graph are 1, 2 and 3, the actual values obtained for t are 100 s, 200 s and 300 s

• Any processed data (eg. averages) should be in columns to the far right
• All units should be in the table headings, not in the body
• Any raw data should be recorded to the resolution of the measuring instrument
• All data of the same type must be recorded to the same number of decimal places

• An example table and graph is shown below for a Velocity v Time graph:

The convention for labelling tables and graphs

Graph Conventions

• When labelling graphs:
  • The independent variable should be plotted on the x-axis
  • The dependent variable should be plotted on the y-axis

• Each axis should be labelled with the quantity and unit, separated by a forward slash just like the table headings
• The graph must cover over 75 % of the space provided
  • This means either axis does not always have to start at 0

• The only exception to this is that a y-intercept must always be read from an axis that starts at x = 0
• A suitable scale must be used for each axis to provide this (in steps of 1, 2, 5 or a multiple of 10)
• When calculating a gradient, draw a triangle that covers at least 75 % of the data points
• Similar to table headings, powers of tens may also be included with the unit on the axes labels, such as t / × 10² s
• The data points should be made with a small sharp pencil
  • The general convention is to put an 'x' instead of a dot, as this is clearer to see on graph paper

• A line of best fit should have roughly equal points on either side and should not be forced through the origin
  • It must also be a thin line that is clear, drawn using a straight edge or ruler

An example of a correctly labelled and plotted graph