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:


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