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

Demand    MADt

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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