Elementary Statistics – Association Examples
(Note: In some of these, and
other real-world, examples, there is not necessarily one right answer.)
- There is a strong positive correlation
between the life expectancy of a nation’s people and the number of television
sets per capita. The U.S.,
for example, is high in both variables, and Rwanda is low in both. Does TV
cause longer life? (If so, we could increase the life expectancy in Rwanda by
shipping a large number of TV sets to them.) Or is there another explanation
of this association?
- A researcher is interested in whether
breast-feeding helps increase a baby’s alertness. She finds a group of
women who breast-feed their babies and a group of women who do not
breast-feed, and she studies them. She finds a strong positive association
between breast feeding and baby alertness. Can she necessarily conclude
that breast-feeding causes a higher level of alertness? Are there other
possible explanations of this association?
- A 1975 survey by the National Center
for Health Statistics showed that the larger the hospital, the longer the
average patient stays. The average stay was 6.3 days in hospitals with
less than 100 beds, and 8.8 days in hospitals with 500 or more beds.
Comment on this association (there may be multiple ways the association
can be explained).