Alpha emission in an atom reduces its atomic number by two. An alpha particle is actually the nucleus of a helium-4 atom.   In alpha decay, atomic number decreases by 2, and atomic mass decreases by 4.  .   An alpha particle is two protons and two neutrons, this is the same as a helium nucleus.
On most PraxisÂ® tests, each selected-response question answered. correctly is worth one raw point, and your total raw score is the. number of questions answered correctly on the full test. Selected-. response questions are scored by computer.
DEFINITION of 'Z-Score'. A Z-Score is a statistical measurement of a score's relationship to the mean in a group of scores. A Z-score of 0 means the score is the same as the mean. A Z-score can also be positive or negative, indicating whether it is above or below the mean and by how many standard deviations.