1. Below showing sales for the past 7 quarters.
Sales
2013 Quarter 4 → 153
2014 Quarter 1 → 117
2014 Quarter 2 → 162
2014 Quarter 3 → 108
2014 Quarter 4 → 144
2015 Quarter 1 → 171
2015 Quarter 2 → 153
a. Using a three-quarter moving average model, calculate the forecast for 2015 Quarter 3 sales.
b. Use the last four quarters as the basis for determining the historical MAD assuming that a three-quarter moving average model was used to forecast sales. For example, the forecast for 2014Q3 would be 144 resulting in an absolute deviation of 36 (now, calculate the forecasts and absolute deviations for 2014Q4, 2015Q1, and 2015Q2, then average the four absolute deviations to get your MAD).
c. Predict the range of 2015 Quarter 3 sales using your forecast and your MAD. The range should include actual sales with 95% confidence.
And for each question my answers are as follows:
a. Forecast for 2015 Quarter 3 sales is 156
b. MAD is 24.
c. Range of uncertainty is from 96 to 216 for 2015 Q3.
Does my answers seems accurate?
If not, can you please guide me how to approach the questions?