Hi Sid, Sorry for a delayed response. I couldn't work in the whole previous week; was sick. I am eager to see how the information provided would affect the model developed: Q: This a field study or a lab study? A: It was a field study. Q: What are your TRTs? A: The treatments are four different corn hybrids belonging to distinct maturity groups. The same set of four hybrids were seeded at two different times (4x2=8 treatments, 1 to 4 (early seeding & 5 to 8 (late seeding). The identity of Treatment 1 to 8 remains unchanged throughout the experiment. Q: What is the experimental unit to which a level of TRT is randomly assigned? A: Corn cob (s) in a treatment is the experimental unit which was measured for its moisture content repeatedly. Q: What is a REP? I want to know how a REP relates to a corn cob or clusters of corn cobs. Is a REP the experimental unit to which a level of TRT is assigned? Or is it a block of experimental units? A replication contains a complete set of all levels of treatments (1 to 8). Replication represents one complete experiment and it was replicated four times in both years. So replication is not a block in my experiment. Q: Is each value of MOIST measured on one corn cob, or is it the mean of 10 corn cobs? I'm trying to figure out where "10 corn cobs" works in here. A: Yes, Moist, as given in the attached text file, is an average of 10 readings of a treatment. Q: Is MOIST a percentage? A: Yes, it is. Q: What is TIME (e.g., days?), and what are the levels of TIME? Are the levels equally spaced? A: Time is a week and equally spaced after two weeks of silking. Q: Do you measure MOIST on the same corn cob nine times, or do you use a different corn cob each time? A: Yes, 10 cobs were randomly selected and then marked. Every week/time the same tagged cob was measured for moisture content. Q: Do you use different corn cobs in different years? Do you use different REPs (whatever they are) in different years? Do you use different experimental units for TRTs in different years? A: Yes, different cobs in both years. Because you have to seed a new crop but the same genetics (hybrids) and the procedure as of the previous year were followed. The identity of treatments and replications remained unchanged. Yes, different experimental units (cobs) for treatments in both years. Q: Within each year, are all four REPs run simultaneously or do you run one REP to completion, then the second, then third, then fourth? A: Within each year all four reps run simultaneously. Every week all reps data was collected within a day (three hours). Q: Within each REP, are all eight TRTs run simultaneously or sequentially? A: Within Reps, all treatments were random, not sequential. Your MOIST values are very similar among REPs (i.e., there is very little variability), apart from some notably odd values which might be typos or outliers. In my experience, agricultural data are typically quite noisy, so your data are uncommon in this regard. Your observation is correct and it is because of the device used to measure the moisture content. A care was taken to make the measurement at a time of the day that is not affecting the measurement. As the device measures the wettest spot (fog and dew would influence the measurement). The model for analysis is: proc mixed data=weekly_moisture; class year rep trt time; model Moist = trt|time|year/ ddfm=kr; random rep;*Note I have not nested the rep in year as it gives infinite tvalue in the LSMEAN tables; repeated /subject = Rep (Trt) type= AR (1); lsmeans Trt*Time/slice=time; run; Quit; Thank you very much for your input fridge
... View more
