A plastic Manufacturer tests the tensile strength of different type of polythene material. A sample of three measurements is taken for each material type and data in pounds per square inch are as follows:Â
Type-I: 200 215 218 220
Type-II: 260 255 277 250
Type-III:245 240 270 -
Determine, if the mean tensile strength of the three different types of materials differ significantly.Â
Carry out an ANOVA test, assuming the samples were normally distributed and the variances in the three populations were homogeneous. He selected Anova: Single Factor, then entered the data ranges, selected Grouped By: Rows and set Alpha to 0.05. He selected a suitable output option and then OK.
This returned a table of data as shown below.
The F value calculated was 16.8. This comfortably exceeds the stated critical value (Fcrit) of 4.45, and the probability of obtaining this result by chance (P-value) was calculated as 0.0013 (0.13% to three significant figures); hence we are able to reject the null hypothesis and conclude that there was a significant difference in average between the three samples, since P <0.05.
Comments
Leave a comment