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.
Z Score also known as Standard Score, is the method of calculating how many standard deviations in a data set is above or below the mean. The distance between the mean and a given Z score in every normal distribution cuts off a fixed ratio of the total area below the curve. Z scores are particularly informative when the distribution to which they refer is normal.