Question

Some studies suggest that having a pet can provide positive mental and physical health benefits for the owner. A particular study involving elderly people who lived alone reported that dog owners had lower blood pressure on average than the non dog-owners, with the difference in average blood pressure between the groups statistically significant.

a) In this context, what does “statistically significant” mean?
b) Explain why this study would be an observational study rather than an experiment.
c) Does this result mean that if an elderly person buys a dog that their blood pressure will decrease? Explain. d) Suggest some possible associated confounding variables for this study.

Answer 1

(a)

The term “statistically significant” means that there is clear evidence that on average blood pressure of elderly people having pet dog is significantly lesser than that of elderly people having no pet dog.

(b)

In this study, the researcher merely observed blood pressure of the elderly people living alone after dividing them into two groups as having pet dog or not. He did not hamper or tried to change their living style based on his requirement of study. So, this is an observational study.

Note: This could have been an experiment if the researcher divided few selected elderly people into two random groups and provide pet dog to one group and nothing to other and collect data about blood pressure after few days (or months).

(c)

This result indicates that if an elderly person buys a dog, then it is highly expected that his blood pressure will decrease after certain (enough) time (may be few days or months, but not instantly).

(d)

One possible associated confounding variable may be economic status of elderly people.

As in this observational study, elderly people who are living alone are considered, it may be such that many of them likes to keep pets but can not do so due to economic disability. Obviously keeping some pet incurs some extra expense which might not being able to bear, few may not have pets. Persons with economical difficulty may stay in different tensions and stress which might increase blood pressure. Also, they may not be able to bear daily necessary things like medicines.

On the other hand, people with pet are expected to be economically more stable. It may be so that they take regular medicines to keep their blood pressure control as well as they are free from few tensions and anxiety.