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.
What is a 'Z-Score'. A Z-score is a numerical measurement of a value's relationship to the mean in a group of values. If a Z-score is 0, it represents the score is identical to the mean score. Z-scores may also be positive or negative, with a positive value indicating the score is above the mean and a negative score indicating it is below the mean.