For questions 7 and 8, state whether the investigation is an observational study or a designed experiment. Explain your answer.7. Researchers randomly assigned 39,876 initially healthy women 45 years of age or older to 100 mg of aspirin or placebo on alternative days and then monitored them for 10 years for a first major cardiovascular event (i.e. nonfatal myocardial infarction, non-fatal stroke, or death from cardiovascular causes).8. A study involving 3800 people over the age of 65 in East Boston. The study took place over a six year period and compared the age at which death occurred for right handed people vs. left handed people among the 3800 people who died during the six year period. The study concluded there was no difference.

Step-by-step explanation: Conducting researches may be structured as being observational or experimental. The difference between the two methods lies thus ;

Observational study requires that subjects or variables employed in the research study are data collected from a source or variables which aren't tampered with during the course of the research study. Here, variables or subjects are not subjected to any treatment before inference is made. Such is the case in scenario (8) whereby inference was made after observing variables involved in the research for 6 years without applying any treatment to either variable before inference was drawn or made.

Experimental design however, involves the actual application of treatment on the subjects involved in the study and their response being noted in other to make a conclusion. The groups may be divided into two ; the treatment group and the placebo group just like in the scenario above.