Which statement accurately describes the Doppler effect? It was used by Hubble to measure velocities of galaxies.

It indicates galaxy motion through changes in sound waves.

It indicates a galaxy moving toward Earth through red shift.

It indicates a galaxy moving away from Earth through blue shift.

Answer is A

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.

the answer would be in this answer. someone already asked the question.