# Independence (1 of 5)

**Independence of Variables**

Two variables are independent if knowledge of the value of
one variable provides no information about the value of another
variable. For example, if you measured the two variables height and
memory ability in a population of adults in the United States, these
two variables would in all likelihood be independent. Knowing
someone's height would not give you a clue about their memory
ability. However, if the variables were height and weight, then there
would be a high degree of dependence. When two variables are
independent then the Pearson's

correlation
between them is 0.

**Independence of Observations **
Two observations are independent if the sampling of one observation
does not affect the choice of the second observation. Consider a case
in which the observations are not independent: A researcher wishes to
estimate how much people engage in shoplifting. The researcher
randomly chooses one person to call and interviews him or her. The
researcher then asks the person who was just interviewed for the name
of a friend so that they can be interviewed next.