5.8 Birth month and health. A Columbus Dispatch article reported that researchers at the Columbia University Department of Medicine examined records for an incredible 1.75 million patients born between 1900 and 2000 who had been treated at Columbia University Medical Center. Using statistical analysis, the researchers found that for cardiovascular disease, those born in the fall (September through December) were more protected, while those born in winter and spring (January to June) had higher risk. And because so many lives are cut short due to cardiovascular diseases, being born in the autumn was actually associated with living longer than being born in the spring. Is this conclusion the result of an experiment? Why or why not? What are the explanatory and response variables?