Q:  Do the RR Lyrae stars cover a wide range of apparent magnitudes,
            or do they all have roughly the same apparent magnitude?

                The colored symbols are grouped together
                in a region roughly 

                     14.5  <=  apparent mag  <= 15.0
 
                which is a pretty narrow range.


  Q:  What does that imply about the range of ABSOLUTE magnitudes
            for these RR Lyrae stars?


                 Since all these stars are at the same distance
                 from us, the absolute magnitudes are equal to 
                 the apparent magnitudes plus some constant offset
                 called the "distance modulus":

                      (m - M)  =  distance modulus
 
                 The distance modulus is related to the distance like so:

                      (m - M)  =   5 * log(d)   -   5


                 The fact that the apparent magnitudes have a narrow range
                 means that the ABSOLUTE magnitudes also fall within
                 a narrow range.