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.
The Z score is just a quantity that you compute by scaling your sample. It is also called a standard score. It is defined via the following formula: [math]Z(X):=\frac{X-E[X]}{sd(X)}[/math], where: [math]E[X][/math] is the expected value of the random variable [math]X[/math].