How can a scientist ensure that his or her data are reliable? by making a single observation

Hi!

We make sure data is reliable by repeating it over and over and over and over and over again! 

Repetition and replication are key, as the most constant consistent results we get - the more reliable the data is!

Hopefully, this helps! =)

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 .