This is the data for the questions I copied it from an excel

This is the data for the questions. I copied it from an excel file. You have 162 monthly values of retails sales of hardware stores (HW) in the US.

a) Estimate and report a linear trend component for the HW time series using the ordinary least squares (OLS) technique.

b) Compute a seasonal index using a 12 month centered moving average fo the HW series. Based on your results, would you describe hardware as a seasonal business? Explain.

c) Do an in-sample forecast on Books sales using the multiplicative time series technique (assume the cyclical component is equal to 1 for every month).

d) Use the information contained in the following table to perform a forecast of HW for November and December 2015 using the multiplicative time series technique (Note: you will need to compute a trend comonent for these months using the equation you obtained in a.

Solution

Are you looking for a holt-winters forecast? I am not sure as to what do you mean by HW time-series

However, this video may help if you are looking for holt-winters method.

https://www.youtube.com/watch?v=qpiWJaeJPtA

If you have further doubts or need clarifications, feel free to ask.