I working on the experiment which has Randomized Complete Block Designs. My experiment consist of three 28 d consecutively periods. I analyzed my data for each period and also in overall by using PROC GLM in SAS. I want to know how I can add “ time effect ” in my analysis?? Does somebody have the SAS code about time effect?
It depends on how you did the experiment, and how time in influencing the results.
If you set up 60 plants, and then took 20 of these at each 28 d interval, then you can enter time into your model as another independent variable, subject to all the assumptions that such variables entail.
if you took 20 plants and measured them all over and over again, then this is more like a RCBD within a repeated measures design. That said, you have to be careful because the repeated measures is trying to correct your data for the correlation inherent in repeated measures. Yet with sufficient time (28 d may or may not be sufficient) the expected correlation will be swamped by the noise from other factors. My body weight today is highly correlated with my body weight tomorrow, but not so much with my body weight 25 years from now. This correlation effect means that knowing my weight on two consecutive days adds little information over knowing my weight on one of those days. In addition to an autocorrelation effect, time introduces a seasonal component that is a dummy variable for day length, sunlight, temperature, relative humidity, rainfall, seasonal succession, and many other factors.
To have any chance of getting the SAS code that you need, you need to provide many more details on your experimental design/protocol.
I truly appreciate for you comment
I working on project about study on different levels of digestible TSAA on quantitative and qualitative traits of egg production during 32 wk to 44 in layer hen.
I have 5 block and 5 treatment with 5 replicate. At the conclusion of each 28d period, I measure some parameters, like feed intake, feed efficiency, egg index, yolk color, protein yield of albumen and yolk and etc.
In overall view, how I can evaluate the effect of time on my parameters that I mentioned during this 12 wk ??
If you want to add time effect, you can analyze your data using MIXED procedure accounting for repeated measures. In fact day of sampling is fixed effect...!
Thank you so much dear Ali razzaghi
I wish bests for you
- Badges
- Science topic
- Similar topics
- Clinical Pharmacology
- Dosing