2 secular trend refers to the general tendency of the

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2) Secular trend refers to the general tendency of the data to grow or decline over a long period of time. 3) Seasonal variation refers to any kind of variation which is periodic in nature and repeats within short duration. 4) Cyclical variation refers to recurrent up-and-down movements around secular trend levels. 5) Irregular variations is also called as erratic is also called as erratic, accidental (or) random variation. 19.5. INTEXT QUESTIONS 1) Explain the meaning and importance of time series. 2) Explain clearly the different components into which a time series may be analyzed. 3) Explain briefly the additive and multiplicative models of time series. Which of these models is more popular in practice and why? 4) What are the advantages and disadvantages of trend analysis? 5) Describe the moving average and least squares methods of measuring trend in time series.
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199 19.6. SUMMARY When we observe numerical facts of an individuals or population at different points of time, the set of observation constitute a time series. The object of time series is to investigate the cause for the present development and on the basic of the present, estimate the future trend. Time series is affected by various changes or movements. These changes or movements are described and measured through time series analysis. There are four basic types of variations and are called as components. They are secular trend, seasonal variation, cyclical variation and Irregular variation. Trend has been measured to find out the growth factor, the rate of change and also estimate the future on the basis of growth factor. 19.7. TERMINAL EXERCISES 1) What is a time series? 2) What is secular trend? 3) What do you mean by seasonal variate?. 4) What is secular trend? 5) What are the components of time series? Choose the correct answer 1) A component of time series used for short term forecast is a. trend b. seasonal c. cyclical d. irregular 2) In an additive time series model, the component measurements are a. positive b. negative c. absolute d. none of these 3) A time series consist of a. two components b. three components c. four components d. five components 4) Method of least square to fit in the trend is applicable only if the trend is a. linear b. parabolic c. both (a) and (b) d. none of the above. 5) Irregular variations in a time series are caused by a. lockouts and strictly b. epidemics c. floods d. all the above 19.8. SUPPLEMENTARY MATERIALS 1) 2) 3) 4)
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200 19.9. ASSIGNMENTS 1) Fit a trend line to the following data by the free-hand method Year 1980 1981 1982 1983 1984 1985 1986 1987 1988 Profit (Rs thousand) 120 150 140 160 130 180 150 170 140 2) Fit a trend line to the following data by the method of semi averages.
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