the college of business was interested in comparing the attendance for three different class times for a business statistics class. the data follow. day 8:00 a.m. class 9:30 a.m. class 11:00 a.m. class monday 25 30 25 tuesday 30 32 30 wednesday 32 35 40 thursday 32 40 39 friday 35 33 30 what is the blocking variable?