Science Buddies: "Ask an Expert"

I have a quick question regarding the experimental design and the dependent variable.

I am to investigate the amount of RDS (Rapidly Digestible Starch) in relation to the retrogradation temperature but what I will measure is the amount of glucose after chemical digestion and I will calculate the amount of RDS by subtracting the amount of free glucose.

In this case, can I say that the RDS is the dependent variable of the experiment because I am looking at the relationship with that?

I was not sure if the dependent variable has to be the thing measured in the experiment or it can be the calculated value from the experiment.

Thank you so much for your help!

Hi and welcome to Scibuddies. Your question is a good one and I hope that other experts will weigh in on it too. My response would be to say that your dependent variable has to be that compound that is of interest to you--the RDS in your case. Often in an experiment we have to measure not the the compound that we want to know the concentration of but something that we have proven is equivalent to it. But, I would still say that the dependent variable is the compound of interest, not what was actually measured.

I emphasize that this is my opinion because I don't have the authority to be positive about it. I hope others will chime in, hopefully with some evidence to back up their statements, as to which compound should be called the dependent variable in your experiment. In your methods write-up you would make it clear which compound you were interested in and which one you actually measured to determine the compound of interest. In my experience, scientific papers rarely use the words 'dependent variable'. In the methods section, it is clearly described what is being measured and how, and it is left to the reader to understand the connection between the measured compound and the compound of interest.

Hope this helps,

Sybee