Mr. Tux rental stores,is begenning to forecast his most important business variable,monthly dollar sales(see the Mr.Tux cases at the ends of chapter)one of his employees,Virginia Perot has gathered the sales data shown in case 2-2.john decides to use all 96 months of data he has collected. He runs the data on Minitab and obtains the autocorrelation function shown in Figure 3-2.5. Since all the autocorrelation coefficients are positive and they are trailing off very slowly,john concludes that his data have a trend.
Next,John asks the program to compute the first differences of the data. Figure3-26 shows the autocorrelation function for the differenced data.The autocorrelation coefficients for time lags 12 and 24,r12=.68andr24=.42,respectively,are both significantly different from zero
Finally,john uses another computer program to calculate the percentage of the variance in the original data explained by the trend,seasonal,and random components
The program calculate the percentage of the variance in the original data explained by the factors in the analysis:
Mr. Tux rental stores,is begenning to forecast his most important business variable,monthly dollar sales(see the Mr.Tux cases at the ends of chapter)one of his employees,Virginia Perot has gathered the sales data shown in case 2-2.john decides to use all 96 months of data he has collected. He runs the data on Minitab and obtains the autocorrelation function shown in Figure 3-2.5. Since all the autocorrelation coefficients are positive and they are trailing off very slowly,john concludes that his data have a trend.
Next,John asks the program to compute the first differences of the data. Figure3-26 shows the autocorrelation function for the differenced data.The autocorrelation coefficients for time lags 12 and 24,r12=.68andr24=.42,respectively,are both significantly different from zero
Finally,john uses another computer program to calculate the percentage of the variance in the original data explained by the trend,seasonal,and random components
The program calculate the percentage of the variance in the original data explained by the factors in the analysis:
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