I need to find a dataset to make an exercice, they do not told me what dataset to use for doing statistical analysis, just to find one....but i don't have experience in this area...there is something in the NCBI or a reliable webpage to download biological datasets to do this type of work? that contains variables, etc to make regression, ANOVA, etc.
I don't know about specific biological datasets. But if it's just to demonstrate the method, why not simply use one of the many R - inbuilt datasets? Just run data() and choose a set that satisfies your needs.
I strongly agree with @Jwvz001 though you could also find a more "real-life" dataset by using Google Dataset Search:
Be aware though, that these datasets can be difficult to import into R and you might also need to clean the data before doing statistical analysis; hence why I agree with @Jwvz001 that for demonstration purposes, R inbuilt datasets are probably what you want.
Yes, indeed that was one of my questions to my professor but the objective of the exercice is to do that, but no one gave us a webpage or information to find this type of databases