Year Quarter Number

Sold

$1$

$16$

$215$

$310$

$44$

$2$

$510$

$618$

$715$

$87$

$3$

$914$

$1026$

$1123$

$1212$

$4$

$1319$

$1428$

$1525$

$1618$

$5$

$1322$

$1434$

$1528$

$1621$

$6$

$1324$

$1436$

$1530$

$1620$

$7$

$1328$

$1440$

$1535$

$1627$

$1.$ Construct a time series plot and develop linear trend equation using the original data

$($with seasonal components$).$

$2.$ Calculate $4-$quarter moving average values for this time series $($column E$).$

$3.$ Calculate centered moving average values and seasonal values $($column F and G$).$

$4.$ Calculate seasonal indexes $($column J$)$ for the four quarters.

$5.$ Copy seasonal indexes $($column J$)$ to column O$,$ and calculate de$-$seasonalized number

sold $($column P$).$

$6.$ Construct a time series plot and develop linear trend equation using the de$-$seasonalized

data $($without seasonal components$).$

$7.$ Calculate trend forecast in year $8$ based on the linear trend equation.

$8.$ Copy seasonal index and compute quarterly forecast values $($re$-$seasonalize$).$