# 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

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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

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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

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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

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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