The number of plumbing repair jobs by Joy Plumbing Service in each of the
last nine months in Miami town are listed below:

Month Jobs
March
April
May
June
July
August
September
October
November
353
387
342
374
396
409
399
412
408
Required:
(i) Forecast the number of repair jobs Joy Plumbing Service will perform
in December. Use the least squares method.
Note:
Slope = (n

tYt
– 
t

Yt
)/n

t
2
– (

t)2
and
Intercept =
Y – bi
t
(8 marks)
(ii) What is your forecast for December using a three-period weighted
moving average with weights of 0.6, 0.3 and 0.1. How does it compare
with your forecast from part (i) above? (4
marks)