HOW TO SET UP AN APPROPRIATE SCALE ON A GRAPH

1.  Look at your data.  Find the largest number that will be plotted on the x axis.

2.  Count the number of boxes there are across the x axis.  (If you are using graph paper, count the number of boxes from where the y axis will be to close to the right side of your paper.)

3.  Divide the largest number on the data table by the number of boxes.  (Usually, this will be a number with a lot of places to the right of the decimal point.  To make it easier, you should probably round up.  The number you round to should be what each line represents.)

4.  Find the largest number among your data to be plotted on the y axis.

5.  Count the number of boxes on the y axis.

6.  Divide the largest number on the data table by the number of boxes.  Round up as appropriate.

EXAMPLE:  I am using the graph paper that is linked to the Periodic Trends in Atomic Radius activity.

On the x axis, atomic number is plotted.  The highest atomic number given on the data table is 54.

The number of boxes across the paper is 30.

54 divided by 30 is 1.8.  I am going to have each line represent 2.  (When I graph my data, there will be points that are in the middle of boxes.  This is OK.)

On the y axis, atomic radius is plotted.  The highest atomic radius given on the data table is 2.16.

The number of boxes down the page is 40.

2.16 divided by 40 is 0.054.  I am going to have each line represent 0.06.

By setting up scales for your graph this way, you use most of the graph.  It also allows for the most accurate graphing of your data.  Doing this is especially important in Physics.