07. Graphical Analysis tutorial.doc
Daley 1 10/9/09
Introduction to Graphical Analysis
In chemistry and physics we often make graphs to show the relationship between two variables. If
the relationship can be modeled by a mathematical function we have a powerful tool for analysis of
the data. You should be familiar with this type of analysis for linear data sets of the form y = mx + b.
Here the dependent variable, y, is related to the independent variable, x, through the slope, m, of
the line and the y-intercept, b. A linear regression fit (best fit) to the data yields a numeric value for
the slope and the y-intercept.
Graphing of Linear Data USING GRAPHICAL ANALYSIS SOFTWARE – 3.04
Graphical Analysis is a easy to learn, inexpensive software program for the MAC or PC. We use this
program extensively in chemistry 1B and 1C. More information about the program can be found at:
http://www.vernier.com/soft/ga.html A complete user’s manual can be downloaded from the vernier
website. At the back of this tutorial is a one-page reference guide provided by vernier.
Aside from simple graphing of data, Graphical Analysis has built-in spreadsheet functions that we
will use in this tutorial to change the raw data into a more suitable form for graphing. From now on,
GA will be used in place of Graphical Analysis.
As a tutorial example, I will use data we collect in chemistry 1B laboratory. The data pairs consist of
temperature of a trapped air sample (x value) and the height of the trapped air sample in a capillary
tube (y value). This data is used in chemistry 1B to illustrate the gas laws, specifically how gas
volume is related to temperature. The raw data a student would collect in lab is given below in Table
I. In the following paragraphs, the screen shots are for the Mac version of Graphical Analysis.
The PC version has slightly different menus but the same functionality.
Table I. Gas Law Data
Step 1.
First enter the
data into GA.
Next double-
click a column
to open up the
Column
Options dialog
box. Change
the X column
heading to
Temperature
with units of
°C (see
picture) and the Y column to Height of air column with units of mm.
Notice in GA the units are entered below the column name. Ignore
the Short Name for now. After you have entered these values the data set should look as shown.
Temperature
(°C)
Height of air
column (mm)
83.5
68.0
82.4
67.0
76.6
66.0
71.7
65.0
64.4
64.0
57.1
63.0
54.7
62.0
47.9
61.0
44.7
60.0
37.7
59.0
33.1
58.0
28.0
57.0
23.9
56.0
20.6
55.5
