The table below demonstrate the demand for Fidgets over an eight month period. Calculate a four-period moving average forecast for September. Also evaluate the quality of the four-period moving average forecasting model by calculating the root-mean-square error for the data set. Note: Round all intermediate calculations to two decimal places.
Month Demand
Jan 10
Feb 11
Mar 5
Apr 8
May 6
Jun 11
Jul 5
Aug 11