Time series analysis involves analyzing data collected over time. A time series is a set of observations made at regular intervals. There are four main components of a time series: secular trend, seasonal variation, cyclical variation, and irregular variation. Time series analysis has applications in forecasting, such as for economic forecasting, sales forecasting, and stock market analysis. Techniques for time series analysis include Box-Jenkins ARIMA models, Box-Jenkins multivariate models, and Holt-Winters exponential smoothing.