# Operations mgmt with std dvd 9e – problems set

The manager of a travel agency has been using a seasonally adjusted forecast to predict demand for packaged tours. The actual and predicted values are as follows:

Period  DemandPredicted
1138        111
2194        200
3157        150
491        94
595        80
6132        144
7126        128
8127        124
995        96
10149        150
11104        94
1285        75
13120        140
14134        128
________________________________________

a.Compute MAD for the fifth period, then update it period by period using exponential smoothing with α = .1.(Round your intermediate calculations and final answers to 3 decimal places.)

t
PeriodA
1138
2194
3157
491
595

6132

7126

8127

995

10149

11104

1285

13120

14134

________________________________________

b.Compute a tracking signal for periods 5 through 14 using the initial and updated MADs. (Negative values should be indicated by a minus sign. Round your intermediate calculations and final answers to 3 decimal places.)

t
PeriodA
DemandTracking
Signal
1138
2194
3157
491
595

6132

7126

8127

995

10149

11104

1285

13120

14134

________________________________________

Checkout time at a supermarket is monitored using a mean and a range chart. Six samples of n = 20 observations have been obtained and the sample means and ranges computed:

SampleMeanRangeSampleMeanRange
13.06.4243.13.46
23.15.4453.06.46
33.11.4163.09.45
________________________________________
Q 2,
Factors for three-sigma control limits for  and R charts

FACTORS FOR R CHARTS
Number of Observations in Subgroup,
nFactor for
Chart,
A2Lower
Control Limit,
D3Upper
Control Limit,
D4
2           1.88         03.27
3           1.02         02.57
4           0.73         02.28
5           0.58         02.11
6           0.48         02.00
7           0.42         0.081.92
8           0.37         0.141.86
9           0.34         0.181.82
10           0.31         0.221.78
11           0.29         0.261.74
12           0.27         0.281.72
13           0.25         0.311.69
14           0.24         0.331.67
15           0.22         0.351.65
16           0.21         0.361.64
17           0.20         0.381.62
18           0.19         0.391.61
19           0.19         0.401.60
20           0.18         0.411.59
________________________________________

a.Using the factors in the above table, determine upper and lower limits for mean and range charts.(Round your intermediate calculations and final answers to 4 decimal places.)

Upper limit for mean
Lower limit for mean
Upper limit for range
Lower limit for range
_______________________________________
b.Is the process in control?

Yes
No

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