Hi there, I was looking for some help if possible.

So, I have a theory that some sharks eat blue fish. I checked 100 sharks. I found out that 30 ate blue fish. 70 did not.

What analysis can I run in RStudio to test this hypothesis and get a p-value (or the null, which I suppose is: no sharks eat blue fish)?

Initially I ran a chi-squared test and got a nice low p-value - 0.00001. But then I got confused... what if 50 sharks had eaten blue fish... now my p-value is 1. Is a chi square test inappropriate here? What can I do to test this simple hypothesis? I have yes/no data for the 100 sharks.

Any info would be really appreciated! Thanks