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Algebra 1 Causal Relationships
1) There is a strong positive relationship between the number of television sets per person in a
country (x) and the life expectancy in that country (y).
The idea of causation is that by changing x we can bring about – or cause – a change in y.
So, could we increase the life expectancy in Cambodia by giving all Cambodians at least two
TVs each?
What is the lurking variable in this situation?
2) Ice cream sales and the number of shark attacks on swimmers are correlated. Determine
whether the quantities have a causal relationship. If they do not have a causal relationship,
identify the lurking variable.
3) A group of students believes that herbal tea has remarkable powers. To test this belief, they
make weekly visits to a local nursing home, where they visit the residents and serve them herbal
tea. The nursing home staff reports that after several months many of the residents are more
cheerful and healthy. A skeptical sociologist commends the students for their good deeds but
scoffs at the idea that herbal tea helped the residents. Explain what lurking variable that accounts
for the observed association.
4) The number of cavities in elementary school children and vocabulary size have a strong
positive correlation. Determine whether the quantities have a causal relationship. If they do not
have a causal relationship, identify the lurking variable.