Just a few comments. To use a statistical design you will need to use replication.

To do an experiment you need to use a randomized application of treatments in your study. You do not mentioning your response variable? What are you expecting to be the values and the effect size of the difference between these combinations.

If you are expecting a lot of variability you will need more replication. If you are expecting the time of day or the order of the treatments to effect the outcome you will need to use a blocked design. These are all terms that you will understand with some reference to the experimental design literature (Roger Mead has a good text)

If there are replicates and you have the 2 factors ( pressure and time) , you can use Completely Randomised Design. Each treatment combination is replicated within the design the same number of times.

In experimental design there is an essential assumption that you randomised the treatments, to avoid bias. SPSS is one option, but do consider using R and RStudio. It is worth the investment of time if you plan to work in research.

Hi Miranda, I do have replicates of each treatment (6 pressure and time combinations) and I have analysed these samples for all kinds of properties including physical and chemical. I do not know what kind of effect the treatment will have on samples as that's what I am trying to find.

I have used randomization during treatment and analysis as well.

I just want to know how can I determine the effect of pressure and time on my samples. However, I also have a control sample which I want to include in my comparison. If I use a randomized complete block design, I cannot include the control in my experimental design as it does not have 2 time points like all of my other samples.

Is there a way to include the control sample in my design to compare it with other samples ??

You need to analyze your given data using factorial experiment design 2×3. You can do it using SPSS by following this link: https://www.slideshare.net/mobile/AlmaszabeenBadekhan/23-factorial-design-in-spss

I hope this will be useful

Dear Safaa, thank you so much for the link. I will have a look into this method and try to replicate it for my data.

However, I have another question, I also want to add my control sample in the statistical analysis. my control sample was untreated and thus do not have 2 time points like all other samples. How can I compare it with all of my other samples?

Dear Prakhar

In this case, you have to create a new level (t0, k0) which prefers to time zero and zero pressure. Now will get an experiment 3×4 (t0,t1,t2) and (k0,k1,k2,k3). You will expect to get significant differences between groups based on F test. If so, I am sure you need to get answer to the following question. Which is the treatment that has effect. The answer is you need to use LSD test. this test explain the individual difference between groups or treatments. I hope this will helpful. best wishes

You are dealing with what is called a dangling control group. I like to think of this type of problem as one of writing contrast statements.

Assign contrast coefficients such that he fastest moving (changing) levels are those of the last factor that was specified, the second fastest moving (changing) levels are those of the next to the last factor, and so on. The coefficient that refers to the isolated control group is always entered as the last one.

Mary Marion