Time SerieIntroduction of Time series: Time never stop, it goes continuously ahead. Change occurs voluntarily in all field with time to time. No field of life is untouched to this changes. Time factor affect political social economic and business various areas with chronological movement. Study of this changes is business, commerce, trade and other field is necessary for economical analysis as well as for all group of society. Changes linked with time factors affect various economic aspects. For the analysis of these changes, analysis of time series technique is used.Meaning of Time Series: Time series is also called historical series and chronological series. The statistical data presented in arranged way on the basis of time, day, month, year, etc. is called a time series. There are two types of variables in time series.Importance of Time-Series Analysis: In present time analysis of time series is important to all categories of society. The whole society is effected by the changes occurs in business, commerce, trade, production, price, etc. Therefore, consumer's, farmer's, traders, businessman, Government and economist all are interested to study and analysis of time series. Main importance of time series are as follows:(1) Helpful in Understanding the Past Transactions(2) Helpful in Forecasting and Planning(3) It helps in Evaluation of Current Achievement(4) It helps in making Comparative StudiesCauses of Variations in Time-series Data:1. Period2. Nature3. Causes of Creature4. RegularitiesComponents of Time Series1. Long Term or Secular Trade2. Short-time Oscillation: i. Seasonal Variationsii. Cyclical Fluctuations3. Irregular or Random Fluctuations:i. Episodic Movementii. Accidental MovementAnalysis of Time-seriesMathematical Model1. Multiplicative Model: O = T x S x C x I Where, O = Original data T = Trend, S = Seasonal Variations, C = Cyclical Variations I = Irregular Movements 2. Additive Model: O = T + S + C + IMeasurement of Secular Trend: Following are the various methods of measuring secular trend:1. Free hand curve method 2. Semi-Average method 3. Moving Average method 4. Method of Least SquaresSome Important Practical for Revision.