What is the control of a science project?

If you are testing 4 different humans and 4 different canines pH level of saliva at different times of day- what would be the control of this project?What is the control of a science project?
The control is supposed to be a standard that you don't do any thing different to while performing the experiment. In this case, you are checking pH of saliva (sounds gross to me). The control would be either a pH standard or maybe water. The control is supposed to demonstrate that everything else is the same, that your pH measurement system doesn't affect the experiment. I'd use the pH standard buffer 7.0 as a control. You should always standardize the pH meter every time you use it and use at least two pH buffer standards. If you're using pH paper, then you can mix up several buffers to make various pH levels that you might expect and show that your standards actually measure as expected. This way, you can have confidence in your saliva measurements (too gross).What is the control of a science project?
i'm pretty sure the saliva is the control. cuz saliva is saliva. you can look at it from different sources and at different times and its levels might change. but its still saliva.
The different times of the day in which you test the pH levels.
before and after eating