7875
How to slove last 2 question.
2. National Scan, Inc., sells radio frequency inventory tags. Monthly sales for a seven-month period were as follows: Month Sales (000 units)
Feb. 19
Mar. 18
Apr. 15
May 20
Jun. 18
Jul. 22
Aug. 20
a. Plot the monthly data on a sheet of graph paper.
Month
Sales
(000)Units
Feb.
19
Mar.
18
Apr.
15
May
20
Jun.
18
Jul.
22
Aug.
20
b. Forecast September sales volume using each of the following:
(1) A linear trend equation.
t
Y
tY
1
19
19
2
18
36
3
15
45
4
20
80
5
18
90
6
22
132
7
20
140
28
132
542
with n = 7, St = 28, St2 = 140
b
=
nSty – StSy
=
7(542) – 28(132)
=
.50
nSt2 – (St)2
7(140) – 28(28)
a
=
Sy – bSt
=
132 – .50(28)
=
16.86
n
7
For Sept., t = 8, and Yt = 16.86 + .50(8) = 20.86 (000)
(2) A five-month moving average.
MA5
=
15 + 20 + 18 + 22 + 20
=
19
5
(3) Exponential smoothing with a smoothing constant equal to .20, assuming a March forecast of 19(000).
Month
Forecast
=
F(old)
+
.20 [Actual – F(Old)]
April
18.8
=
19
+
.20 [18 – 19]
May
18.04
=
18.8
+
.20 [15 – 18.8]
June
18.43
=
18.04
+
.20 [20 – 18.04]
July
18.34
=
18.43
+
.20 [18 – 18.43]
August
19.07
=
18.34
+
.20 [22 – 18.34]
September
19.26
=
19.07
+
.20 [20 – 19.07]
(4) The naive approach.
20000
(5) A weighted average using .60 for August, .30 for July, and .10 for June.
0.60(20) + 0.30(22) + 0.10(18) = 20.40
c. Which method seems least appropriate? Why? ( Hint: Refer to your plot from part a. )
d. What does use of the term sales rather than demand presume?