A study that involves Statistics will clearly involve a process of data collection. But there are differences in study objectives which are important to recognize. The main distinguishing factor is whether the study aims to find some evidence of a result or whether it aims to find causes of a result. Medical research is a good context to understand these differences - Statistics in medical research is often called Biostatistics.

It is true that many benefits have been detected of taking a low-dosage of aspirin every day. For example, it has been observed that people who take aspirin regularly (less than 300 mg per day) generally have less health problems such as heart attacks, strokes and cancers. The keyword is “observed”: in a community health study involving thousands of people there will be many that take aspirin regularly for problems such as back pain or headaches. For those people it could be observed that they have less chronic diseases compared to people who don’t take aspirin. This is evidence of a difference, but it does not prove that aspirin is the actual cause of the improved health. People who do not take aspirin daily might be poorer and neglect taking medication, and they suffer from more chronic diseases than people with a higher income, so the real difference is socio-economic. From such an observational study it is not possible to conclude a causal effect, it just gives some tentative evidence of a possible relationship between the treatment and the outcome.

In order to be able to prove that aspirin is the cause of the improvement in health, an experiment needs to be conducted where conditions are controlled between those taking aspirin and those not taking it. Such an experiment might be designed as follows, restricted to men, for example, since the effects are suspected to be different for men and women. Suppose we take a large group of men in the age group 60- 70 years of age that have no history of chronic disease. We divide them into two groups so that the groups are “balanced” in terms of known factors such as age, social class, and so on (we don’t want one group to have older men than the other). By the way, this “dividing into two groups” is not a trivial matter, but that is a subject for later in this course. Assuming the two groups are comparable, then one group is given the daily low dose of aspirin and the other not, and the groups are followed up for a five-year period and then compared for the incidence of health problems that develop during this time. If the group taking aspirin has less health problems, this would indicate a beneficial effect caused by the aspirin.

This type of experiment on people has all sorts of problems, but it is really leading to a conclusion about whether aspirin is the real cause of differences between the two groups. There is the ethical problem of not giving the daily aspirin, which has suspected benefits, to a large group of people. There is also the problem that one group knows it is taking the medication and might change their lifestyle to favour a good outcome by living more healthily. This effect can be eliminated by not telling either group what they are getting and giving the non-aspirin group a so-called placebo, which is medication in the form of an aspirin, so both groups think they are getting the medication.

As also understood from the information given, “A study which aims to find some evidence of a result” is an example of observational studies, so the correct answer is A. “A study which aims to find causes of a result”, “A study in which the groups are “balanced” in terms of known factors” and “A study conducted where conditions are controlled” are the examples of experimental studies.