The manager of Petro North gasoline service station wants to forecast the demand
ID: 388548 • Letter: T
Question
The manager of Petro North gasoline service station wants to forecast the demand for unleaded gasoline next month so that the proper number of gallons can be ordered from the distributor. The manager has accumulated the sales data and forecast accuracy measures during the past 10 months, which are shown in the table below. Fill all blank spaces in the table labeled a through f. Month3-month Simple MAD MAPD MSE CE Moving Average (in gallons) Feb Mar Apr May lun Tul Aug Se Oct Nov 1130 440 1670210.00 N/A N/A N/A 310.00 1340.00 1443.33 N/A N/A NIA N/A N/A N/A 8100 N/A N/A NIA N/A N/A NIA -90 240.00 606.67 960.00 790.00 1360 90.00 262.22 262.00 255.71 0.074 0.167 0.159 0.159 58500 1810 1630 1510 1566.671920C0.17294072 1800.00 81038 1470271.11 0.16784245 76021 310.00Explanation / Answer
a =(1810+1920+1630 ) / 3 = 1786.667
b = 1310 - MAD = 1220 OR 1340 =( b + 1440 + 1360) /3 , b = 1340*3 - 1360-1440 = 1220
c = (262.22*3 + 1920 - 1566.67)/4 = 285
262.22 is MAD of 3 observations , so divided by 4. The 4th observation is abs difference between sales and forecast in month of August
d % age for June = (1670-1340)/1670 = 0.197
MAPD , d = (0.074 + 0.197) / 2 = 0.135
e. Sum of square of errors May, June and July = (1310 - 1220)^2 + (1670-1340)^2 + (1810-1443.33)^2 = 251446.89
Mean of sum of errors = 251446.89 / 3 = 83815.62
f) Forecast error, October = 1470 - 1786.66 = -316.67
f = 790 - 316.67 = 473.33
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