QUESTION 1

The value of sales ( 000) of soccer equipment by a large department store is shown for each period of the month as follows:

1989 1990 1991 1992 9 21 30 35 45 65 65 90 82 25 21 30

1. Using an addition model, find the centred moving trend.
2. Find the average seasonal variation for quarter.
3. Predict sales for the last quarter of 1992 and the first quarter of 1993 stating any assumptions.