Karla is training for a marathon she can run 2 miles and 16 minutes if she runs at that pace the whole race how long will it take her to run the entire marathon

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 .