Introduction To Materials Management 8th Edition By Chapman – Test Bank

INDEPENDENT DEMAND ORDERING SYSTEMS
CHAPTER 11
ANSWERS TO PROBLEMS
11.1
Average inventory = 1600 + 100 = 900 units
2
Order point = 4 × 150 + 100 = 700 units
11.2
Average inventory = 10 × 90 + 200 = 650 units
2
Order point = 6 × 90+ 200 = 740 units
11.3
Period Actual
demand Deviation Deviation
squared
1 500 0 0
2 600 100 10000
3 425 −75 5625
4 450 −50 2500
5 600 100 10000
6 575 75 5625
7 375 −125 15625
8 475 −25 625
9 525 25 625
10 475 −25 625
Total 5000 51250
Average demand = 500 units
Sum of the squares of deviations = 51250
Average square deviation = 51250  10 = 5125
Sigma = 5125 = 71.59 units
121
11.4
Average demand = 2000 units
Sum of the squares of deviations = 340,000
Average of the squares of the deviation = 340,000  10 = 34,000
Sigma = 34,000 = 184.39 units
11.5 a. Safety stock = zero
Order point = DDLT + SS = 250 + 0 = 250 units
b. Safety stock = 1.04 × 130 = 135 units
Order point = 135 + 250 = 385 units
11.6 Safety factors taken from Figure 11.5
Service Safety Safety Change in
Level Factor Stock Safety Stock
75 0.67 67
80 0.84 84 17
85 1.04 104 20
90 1.28 128 24
95 1.65 165 37
99.99 4.00 400 235
Period Actual
demand
Deviation Deviation
squared
1 1700 −300 90000
2 2100 100 10000
3 1900 −100 10000
4 2200 200 40000
5 2000 0 0
6 1800 −200 40000
7 2100 100 10000
8 2300 300 90000
9 2100 100 10000
10 1800 −200 40000
Total 20000 0 340000
122
11.7 Orders per year = 10,000 ÷ 750 = 13.33
Service level = 12.33 ÷ 13.33 × 100 = 92.5%
Safety stock = 1.42 × 150 = 213 units
Hint: Use the average of the SF for 90% and 94% i.e. 1.28 and 1.56
Average inventory = 750 ÷ 2 + 213 = 588 units
Order point = 10,000 × 2 + 213 = 598 units
52
11.8 Orders per year = 225 × 52 = 14.625
800
Service level = 15.25 ÷ 16.25 = 93%
Hint use the actual value for the safety factor is 1.47 from tables but
we can use the value for 94% (1.56) and be not far off.
Safety stock = 1.56 × 175 = 273 units
Average inventory = 800 + 273 = 673 units
2
Order point = 225× 3 + 273 = 948 units
11.9 Orders per year = 600× 52 = 12.5
2500
Service level = 11.5 ÷ 12.5 = 92%
Safety stock = 1.42 × 100 = 142 units
Hint use the average of the safety factor for 90% and 94%
Average inventory = 2500 + 142 = 1392 units
2
Order point = 600 × 4 + 142 = 2542 units
11.10
SIGMA (LTI) = SIGMA (FI)
FI
LTI
= 100 √
3
1
= 173 units