Why is June 21 the official start of summer? Let’s see how SQL can help us answer this question. The Summer Solstice Officially, June 21 is recognized as the summer solstice, the longest day of the entire year in terms of daylight. Why? Because on this day, the sun rises early and sets quite late. People in the Northern Hemisphere celebrate the summer solstice with feasts, bonfires, picnics, and traditional dances and songs.
In my previous articles, I dealt with analyses of only a single variable. Now it is time to check whether two variables of interest are independent or somehow related. For example, a person’s height positively correlates with shoe size. Taller people have larger shoe sizes, and shorter people have smaller shoe sizes. You can find this and many more examples of positive associations at: http://examples.yourdictionary.com/positive-correlation-examples.html. A negative association is also possible.