When a data set has an even number of elements, the median is calculated by

Example:
Set of data: 1,2,3,4,5,6,7,8
Cross of 1 and 8, cross off 2 and 7, cross off 3 and 6. Two numbers are left so find the average by adding the two numbers and dividing by 2.
i.e. 4+5=9 and 9/2= 4.5
The median would be 4.5.
In other words the median is halfway between the two numbers.

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 .