The metric system is also known as the

The International System of Units is the current international standard metric system and is also the system most widely used around the world. It is an extension of Giorgi's MKSA system—its base unitsare the metre, kilogram, second, ampere, kelvin, candela and mole.

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .