Do the tested hypotheses concern the actual values of the coefficients (i.e. B), or their estimated values (i.e. f), and why?

The hypothesis tested are concerning the actual values of the coefficients (i.e. \beta) .

Here \beta is our population parameter and \widehat{\beta} is our sample statistic.

A hypothesis test is where we collect a representative sample and examine it to see if our hypothesis holds true for the population. Here, we calculate \widehat{\beta} as an estimate to our true population parameter \beta and thats the reason the hypothesis tested concerns \beta rather than \widehat{\beta} .