A study of the properties of metal plate-connected trusses used for roof support yielded the following observations on axial stiffness index (kips/in.) for plate lengths 4, 6, 8, 10, and 12 in.

4: 328.7 409.5 311.0 326.5 316.8 349.8 309.7
6: 336.8 347.2 361.0 404.5 331.0 348.9 381.7
8: 375.5 366.2 351.0 357.1 409.9 367.3 382.0
10: 419.7 452.9 461.4 433.1 410.6 384.2 362.6
12: 407.2 441.8 419.9 410.7 473.4 441.2 465.8

Does variation in plate length have any effect on true average axial stiffness? State and test the relevant hypotheses using analysis of variance with α = .01. Display your results in an ANOVA table. (Round answers to whole numbers and F to 2 decimal places)

Source Df SS MS F
Treatments
Error
Total