There are certain phenomena that define our society such as population, birth or death rates, incomes, etc. And the one parameter which shows a clear variation in all of these phenomena is time. So, when we plot a collection of readings with respect to a phenomenon against time we call it a series in time. Furthermore, we can also categorize the nature of the trend (upward tendency or downward tendency) which a particular series is displaying. The study of these various series is what we call time series analysis. Let’s discuss it further.