4.Problem 4

The table, below, contains quarterly sales of natural gas to customers in a northern city from 2015 to 2019.

a.Determine the seasonal index for each quarter within the table.

b.Calculate the deseasonalized demands for each quarter.

c. Then use your deseasonalized demands from to build a 3-quarter simple moving average forecast, then re-seasonalize the forecast.

Build a table, for these calculations.

Year Quarterly Avg Seasonal Index Deseasonalized Index

Quarter 2015 2016 2017 2018 2019

I 3661 3781 3660 4141 4154

II 1907 1749 1869 1991 1653

III 1500 1359 1335 1382 1193

IV 2775 2713 3042 2926 2584

Sum: 9843 9602 9906 10440 9584

YearAvg 2460.75 2400.5 2476.5 2610 2396