I would like to analyse the effect of treatment and storage time on vitamin content of cheese. For this, I had made cheese with three different treatments (Treatment A, Treatment B and Treatment C). I stored all the experimental cheeses at 10°C for 90 d. During storage, I had taken cheese samples at 30, 60 and 90 d of storage for analysis of vitamin content. Now, I would like to analyse the effect of treatment and storage time on vitamin content of cheese. Moreover, I would also like to see the interaction effect between treatment and storage time. Note that I had repeated the same experiment two times (i.e. trial 1 and trail 2) with different materials; in another word, the sample size is 2. Which statistical analysis is appropriate for this? Trial treatment storage time(day) vitamin content (µg/100 cheese) 1 A 30 90.17 2 A 30 88.22 1 B 30 106.94 2 B 30 129.93 1 C 30 127.99 2 C 30 120.74 1 A 60 49.72 2 A 60 45.70 1 B 60 67.48 2 B 60 96.57 1 C 60 91.41 2 C 60 104.38 1 A 90 45.19 2 A 90 37.63 1 B 90 63.23 2 B 90 71.03 1 C 90 78.26 2 C 90 84.34 Some of my college suggested me to do split-plot design and the code is: proc mixed data=prabin; class trial treat time; model vitamin = treat time treat*time/ddfm=satterth; random trial trial*treat; lsmeans treat time treat*time/adjust=tukey pdiff; run; Is this a correct statistical analysis? What does the random trial trial*treat means in the code? Thank you very much in advance!
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