the following is the result of a two way anova: source of variation df sum of squares mean square f fcritical treatments (brand) 4 53,231 13307.75 95.56732 3.26 blocks 3 116,218 38739.25 278.1993 3.49 error 12 1,671 139.25 total 19 171,120 what explanation best describes these results?