2. What is the purpose of forecasting? Why are forecasts not always correct? What are the limitations of forecasting? ...

1. What are the components of a time series? What external factors might affect each of the different components? 

2. What is the purpose of forecasting? Why are forecasts not always correct? What are the limitations of forecasting? 

3. Why is the trend commonly thought to be the most important component of forecasting? How is the linear trend method related to linear regression? Why are simple moving averages and weighted averages commonly used forms of forecasting? 

4. What is an index number as relates to time series analysis? In a regression of a time series that states data as a function of calendar year, what requirement of regression is violated? How might one overcome this requirement and still perform a successful time series analysis?