Paul

Let me find an  example and post it by the weekend.

Isaac

Thank you very much. I really look forward to moving forward with this forecasting task and if I can build in assumptions and any known future events - that would be great 

HI Isaac, are you able to advise when you will be able to respond to my query, please? Many thanks Paul 

I received data from a department store. It took me some time to figure things out.

If you look at the sheet Data I tried to chart the data

The only explanation I had was that the variability depends on holidays. See sheet named Data. 

On the regression sheet I prepared the variables for the month with the extra demand based on holidays.

I ran a regression and I found that the standard error was low and the R squares was high.

Attached .

Thanks very much Isaac. I will work through your example tonight. Regards Paul