The main conclusion may be invalid because of the confounding effects of uncontrolled variables
Estimates may be biased because of non-random sampling
Observations have to be taken on groups of individuals rather than on individuals themselves
None of the above
Answer is Wrong!
Answer is Right!
The correct answer is D. None of the above.
All of the options are problems associated with observational studies.
- Option A: The main conclusion may be invalid because of the confounding effects of uncontrolled variables. This is a well-known problem with observational studies. For example, if you were to study the relationship between smoking and lung cancer, you might find that smokers are more likely to get lung cancer. However, this does not necessarily mean that smoking causes lung cancer. It is possible that there is another factor, such as genetics, that is causing both smoking and lung cancer.
- Option B: Estimates may be biased because of non-random sampling. This is another problem with observational studies. If you do not randomly select the participants in your study, then your results may be biased. For example, if you were to study the relationship between education and income, you might find that people with more education tend to have higher incomes. However, this does not necessarily mean that education causes higher incomes. It is possible that there is another factor, such as family background, that is causing both higher education and higher incomes.
- Option C: Observations have to be taken on groups of individuals rather than on individuals themselves. This is a limitation of observational studies. In an observational study, you cannot control the variables that you are studying. You can only observe what happens naturally. This means that you cannot be sure that the results of your study are due to the factors that you are studying, and not to other factors that you have not considered.
In conclusion, all of the options are problems associated with observational studies.