A questionnaire was sent to 34,000 randomly chosen individuals living in USA ask

Question

A questionnaire was sent to 34,000 randomly chosen individuals living in USA asking about their current and past smoking habits. For those who answered the questionnaire, they are tracked in the next 10 year for the death rate. Their data was pulled from the health record database so that if they died, the death is recorded with the diagnosis of the cause of the death. The death rates due to heart disease among the smokers and nonsmokers are then compared to see if smoking causes heart disease. What is the targeted population? What is the sampling population? What is the sample? What are the parameters we are interested in? What are the statistics? Is this an observational study or controlled experiment? Is it possible to draw conclusion from this study that smoking causes heart disease? Why and why not?

Explanation / Answer

(a) Targeted population: Population of the human being.

REASON: The objective of the experiment is to draw conclusion that smoking causes heart disease. This applies to entire human being.

(b0 Sampling population: 34,000 randomly chosen individuals living in USA

(c) Sample: collection of individuals who answred the questionaire.

(d) Parameters we are interested in: numbers of smokers, death rate due to heart disease

(e) What are the statistics: number of smokers obtained from questionaire. Death rate recorded with the diagnosis of cause of the death as heart disease.

(f) This is only observational study. It cannot be cannot controlled experiment.

REASON: The sampling is based on response from a questionaire and the response getting cannot be called purely statistical. So, it cannot be qualified for controlled experiment, we are not controlling the input variables and we are just passive observers.

(g) It is not possible to draw conclusion from this study that smoking causes heart dissease.

REASON:
This is only an observational study but not controlled experiment.

Only a very small small of those responded among 34,000 individuals in USA is considered.

Th correct method is to conduct controlled experiment on the same with stratified sampling from all countries for meaningful results.

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