Q. 4. A two year sales history by quarter for a seasonal product is given below.

Sales

Quarter First Year Second Year

1 30 42

2 48 58

3 60 74

4 35 44

a) Using Winter's method, forecast the quarterly sales for the third year.

b) Assume that the actual sales for the first quarter of year 3 is 48 units.

What is the revised forecast for the second quarter of the third year? Use a=?=?=0.2.

c) Assume the following actual sales occurred during third year.

Quarter Sales

1 48

2 70

3 95

4 50

What is the 95% confidence interval around a one-period forecast?