Page 139 - Data Science class 11
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Example # 1: Chain Smoking and lung Cancer
Sir Richard Doll of the UK’s Medical Research Council, along with others, published a scientific paper that was truly
unprecedented. This happened fifty years ago. In 1951, they asked 40,000 doctors if they smoked. During the next
three years, they compared those answers with information about doctors who went on to develop lung cancer. They
revealed that smoking can cause lung cancer.
It was the first statistical proof that established a link between smoking and lung cancer. The findings were to have
an impact on the minds and lives of millions of people all over the world. The study has formed the basis for research
into the impact of smoking cigarettes on health. It has undoubtedly helped to save millions of lives. The study was the
culmination of years of hard work, all aimed at trying to find out why so many people were dying from lung cancer.
Example # 2: Outcome of eating Organic Diet
An observational study would be used if a researcher wanted to see what effect eating an organic diet has on general
health. The researcher finds 500 individuals, of whom 250 have eaten an organic diet in the past five years, while the
remaining 250 have not had an organic diet in the past five years. An overall health assessment is then performed on
each of these 500 individuals. The results from the health assessment are then analysed, and conclusions are drawn
on how an organic diet can affect one’s overall health.
Non-Example of Observational Studies
Consider the same organic food example as above as an observational study. Let us assume that a researcher finds
200 random people who do not eat organically, and then makes 100 of those people eat organically and lets the
remaining 100 people not eat organically for the next three years. After three years, the researcher would observe
the effects on their overall health.
In such a scenario, the researcher would have to influence these subjects to switch their eating habits. This would
be considered a sort of treatment in this case and no longer an observational study. This is primarily because the
researcher would need to influence the subjects, whereas in the other scenario, the researcher would just observe the
subjects without changing or influencing them.
Observational Study
Example Non Example
Don't Eat
Eat Organically
Organically
J J
J J J J J J
Health J J J J J J
J J J
J J J J J J J J
J Assessment J J
J
J J
J Assign to groups
Don't Eat Organically
Eat Organically Don't Eat
J
J J Organically
J Health
J
J Assessment J J J
J J J J J
J J J J J J J
J J J J
J J J
J J
Health Health
Assessment Assessment
Why observational study when there is a trial assessment?
Sometimes, it may not be possible to perform trial assessments. In such cases, you need to rely upon observational
study for data collection. The reasons behind this are as follows:
Forecasting on Data 137

