ANOVA on Hardness Data
In this activity you will be performing an ANOVA analysis on hardness data to determine whether there is a statistical difference in the hardness of an elastomer when it is exposed to different levels of gamma radiation. Viton is an elastomer that is produced by DuPont Dow. Elastomers are synthetic polymeric substances that have properties like rubber, such as elasticity and flexibility. They are used in military settings as well as on the International Space Station. Data was collected during a CVGS student's experiment exploring the effect of gamma radiation on Viton. The amount of radiation, measured in Megarads (Mrad), was the independent variable and the hardness (Newtons) was the dependent variable.
Gamma radiation is electromagnetic radiation emitted during radioactive decay. It has an extremely short wavelength. Gamma radiation has been found to change chemical and physical properties of materials. Elastomers are used in the nuclear industry for cable trays, sheathing of cable and dampening materials because of their elasticity and flexibility. Hence, nuclear engineers need to evaluate whether gamma radiation affects the physical properties of the elastomers they use.
A durometer test was used
to evaluate whether radiation had an effect on the hardness of Viton.
Three readings were taken from each sample to ensure accuracy. These durometer
readings were then converted to Newtons by the following formula: N=.075x+.55
Using either Excel or the TI-83 graphing calculator, perform a one-way ANOVA test to determine if there is a significant difference between the hardness means of the control, one-, ten-, and fifty-Mrad groups. If there is a significant difference, you will need to determine which means are significantly different by doing a Tukey Test.
The data exists in three files: in Excel Data format, Text format and TI-83 Group format. If you want to perform the ANOVA using the TI-83, you will have to import the text data into the calculator from the computer after you have downloaded the file.
Is there a significant difference in the mean hardness values of the Viton radiation groups? If so, which groups? Does radiation have an effect on the hardness of Viton? What happens to Viton as it is exposed to larger amounts of gamma radiation? Do you think engineers in the Nuclear Industry should be concerned about the effect of radiation in elastomers?
work on this document was done by Central Virginia
Governor's School student Stephen Sims (Class of '05).
Copyright © 2004 Central Virginia Governor's School for Science and Technology Lynchburg, VA