DRAWING LINE GRAPHS

Line graphs are the most common type of graph you draw in Science. They are used when presenting continuous data where two variables are used.

An appropriate line graph should:

· be drawn using a sharp pencil

· have a clear and descriptive title

· display the independent variable on the x-axis (the variable the experimenter purposely changes in an experiment)

· display the dependent variable on the y-axis (the variable which changes in response to changes in the independent variable)

· have axes with a clearly-marked, even scale that increases with even increments

· always have the vertex representing (0,0)

· have a scale which allows the range of data displayed to extend over more than half the grid in both directions (if the data is spread over a small range this can be done by starting at zero at the vertex, using a hash or a zig-zag, then starting with a value close to that of your smallest value)

· have axes labelled with the appropriate quantity

· have axes labelled with the appropriate units

· have accurately plotted points drawn as neat, small crosses

· a line or curve of best fit is required to represent a trend (unless told to not join the centre of each cross)

· have a clear key if more than one line is shown on a graph using different lines (not points) for different data sets

AN EXAMPLE OF A GRAPH

NB. The points in the graph above should be drawn as crosses!

Using the graph to predict results:

1. Interpolation

eg. using the graph predict how many days it would take for the seedling to reach a height of 15 cm. Two lines must be drawn on the graph as shown below.( a line from 15 cm on the y axis until it hits the graph and then a line down to the x axis which will give the expected number of days which is about 3.7 days).

2. Extrapolation

eg. using the graph predict how high the seedling would be after 5.2 days. The line on the graph must be extended as shown and then two lines must be drawn on the graph as shown below (a line from 5.2 days on the x axis until it hits the graph and then a line across to the y axis which will give the expected height which is about 27 cm).

	Created by ClareArmstrong over 12 years ago

Science (Practical) Note on Science Practical Notes, created by ClareArmstrong on 08/05/2013.