1) The S & P/TSX Composite Index is based on common stock prices of a group of Canadian stocks. The weekly close level of the TSX for 6 weeks are shown: Week TSX Index 1 8480 2 8470 3 8475 4 8510 5 8500 6 8480 a) Compute the three week moving averages and forecast the TSX Index forecast for week 7 b) Compute the three week weighted moving averages using 3, 2 and 1 for most recent, second most recent, and third most recent periods. Find the TSX Index forecast for week 7. c) Compute the exponentially smoothed forecasts for weeks 2 to 7 using α = 0.7. d) Calculate the MAD and MAPE for all three methods. Which provides the best forecast for the TSX Index? 2) The following data represents the quarterly piano sales of Sawyer Piano House for 3 consecutive years. Year Quarter Sales (000$) 1 1 4 2 2 3 1 4 5 2 1 6 2 4 3 4 4 14 3 1 10 2 3 3 5 4 16 a) Compute the seasonal indices and normalized indices using overall average sales. b) Compute the seasonal indices and normalized indices using centred moving average sales. c) If the average quarterly forecast for year 4 is $10,000, use the seasonal indices (unnormalized) to calculate seasonally adjusted quarterly forecasts for year 4. 1
3) James Steven has been hired by the Victory Stores, a convenience store, to study how factors such as floor space area, number of parking spaces, and average family income of families in the city affect daily sales. A random sample of 15 stores is obtained and the data are as follows: Sales ($) Floor Area Parking Spaces Income ($ 000) 1840 532 6 44 1746 478 4 51 1812 530 7 45 1806 508 7 46 1792 514 5 44 1825 556 6 46 1811 541 4 49 1803 513 6 52 1830 532 5 46 1827 537 5 46 1764 499 3 48 1825 510 8 47 1763 490 4 48 1846 516 8 45 1815 482 7 43 SUMMARY OUTPUT Regression Statistics Multiple R 0.91397794 R Square 0.83535568 Adjusted R Square 0.79045268 Standard Error 13.4242577 Observations 15 ANOVA df SS MS F Significance F Regression 3 10057.68236 3352.561 18.60356 0.000128518 Residual 11 1982.317643 180.2107 Total 14 12040 Coefficients Standard Error t Stat P-value Lower 95% Upper 95% Intercept 1480.74461 126.3041592 11.72364 1.48E-07 1202.751032 1758.7382 Floor Area 0.73149888 0.163330495 0.000933 0.37201088 1.0909869 Parking Spaces 9.99148739 2.599960572 3.842938 0.002733 Income ($ 000) -2.3082627 1.594675103-1.44748 0.175655-5.818118954 1.2015935 2
a) From the Excel output above determine the regression equation, adjusted coefficient of determination, correlation coefficient, standard error of the estimate. Interpret the meaning of each. b) Interpret the coefficients of each of the independent variables. c) Forecast a sales level for 500 (floor area), 5 (parking spaces) and 50 (Income, 000s). d) Complete the coefficients table by filling in the missing data for t stat (Floor Area) and Lower and Upper 95% confidence limits (Parking Spaces). e) Conduct an overall hypothesis test to determine if the regression equation is significant (useful) in explaining differences in Sales. Use a 5% significance level. f) Conduct individual hypothesis tests to determine which independent variables are significant or should be dropped in explaining differences in Sales. Use a 5% significance level. 4) Complete the following ANOVA table, assuming the sample size is 20. ANOVA df SS MS F Regression 2 18010.21 Residual (Error) 10057.68 Total 3
Definitions and concepts to know 1. Time Series Forecasting 2. Causal Forecasting 3. Qualitative Forecasting (a) Delphi Method (b) Jury of Executive Opinion (c) Sales Force Composite (d) Consumer Market Survey 4. MAD 5. MAPE 6. Trend 7. Seasonal 8. Cyclical 9. Random 10. Moving Average 11. Weighted Moving Average 12. Exponential Smoothing, Smoothing constant or parameter 13. Stationary, Non-stationary 14. ANOVA Table 15. Simple Regression 16. Multiple Regression 17. Correlation Coefficient 18. Coefficient of Determination 19. Standard Error of the Estimate 4
Answers/Solutions 1) a) b) c) Error Actual Week Actual 3 Week Moving Error Error TSX Index Average Forecast 1 8480 2 8470 3 8475 4 8510 8475 35 35 0.0041 5 8500 8485 15 15 0.0018 6 8480 8495-15 15 0.0018 7 8497 Totals 65 0.0077 MAD = 21.7 MAPE = 0.257% Error Actual Week Actual 3 Week Moving Error Error TSX Index Average Forecast 1 8480 2 8470 3 8475 4 8510 8474 36 36 0.0042 5 8500 8492 8 8 0.0009 6 8480 8499-19 19 0.0022 7 8492 Totals 63 0.0073 MAD = 21.0 MAPE = 0.243% Error Actual Week Actual Exponentially Smoothed Error Error TSX Index Forecast α =.7 1 8480 8480 (assumed) 2 8470 8480-10 10 0.0012 3 8475 8473 2 2 0.0002 4 8510 8474 36 36 0.0042 5 8500 8499 1 1 0.0001 6 8480 8500-20 20 0.0024 7 8486 Totals 69 0.0081 MAD = 13.8 MAPE = 0.162% d) Exponential Smoothing provides the best forecast due lowest MAD (13.8) and MAPE (0.162%). 5
2) a) b) Year Quarter Sales Overall Seasonal Seasonal Seasonal Index Average Sales Ratios Index (Normalized) 1 1 4.0 6.17 0.648 1.080 0.270 2 2.0 6.17 0.324 0.486 0.122 3 1.0 6.17 0.162 0.540 0.135 4 5.0 6.17 0.810 1.891 0.473 2 1 6.0 6.17 0.972 Total 3.997 Total 1.000 2 4.0 6.17 0.648 3 4.0 6.17 0.648 4 14.0 6.17 2.269 3 1 10.0 6.17 1.621 2 3.0 6.17 0.486 3 5.0 6.17 0.810 4 16.0 6.17 2.593 Seasonal Ratios Year Quarter 1 Quarter 2 Quarter 3 Quarter 4 1 0.648 0.324 0.162 0.810 2 0.972 0.648 0.648 2.269 3 1.621 0.486 0.810 2.593 Average 1.080 0.486 0.540 1.891 Seasonal Indices Year Quarter Sales Centred Moving Seasonal Seasonal Seasonal Index Average Sales Ratios Index (Normalized) 1 1 4.0 2 2.0 3 1.0 3.25 0.308 0.421 0.110 4 5.0 3.75 1.333 1.556 0.407 2 1 6.0 4.38 1.371 1.321 0.346 2 4.0 5.88 0.681 0.523 0.137 3 4.0 7.50 0.533 Total 3.821 Total 1.000 4 14.0 7.88 1.778 3 1 10.0 7.88 1.270 2 3.0 8.25 0.364 3 5.0 4 16.0 Seasonal Ratios Year Quarter 1 Quarter 2 Quarter 3 Quarter 4 1 0.308 1.333 2 1.371 0.681 0.533 1.778 3 1.270 0.364 Average 1.321 0.523 0.421 1.556 Seasonal Indices 6
c) For Overall Average Year 4 Q1 = 10800 Q2 = 4860 Q3 = 5400 Q4 = 18910 For Centred Average Year 4 Q1 = 13210 Q2 = 5230 Q3 = 4210 Q4 = 15560 In the case of centred average, better to allocate an annual estimate of 40000 with the normalized indices. Year 4 Q1 = 13840 Q2 = 5480 Q3 = 4400 Q4 = 16280 3) a) From Summary Output Regression equation ŷ = 1480.74 + 0.7315x 1 + 9.9915x 2 2.3083x 3 Coefficient of Determination = R 2 = 0.835 Correlation Coefficient = 0.914 Standard Error of Estimate = ±13.424 Meanings - see Practice Q1 and Causal Forecasting Model notes b) For each additional square foot of floor area, we expect sales to increase by 0.7315$, all else being held constant. For each additional parking place, we expect sales to increase by 9.9915$, all else being held constant. For each additional ( 000)$ average income, we expect sales to decrease by 2.3083$ c) $1781 d) t stat (Floor Area) = 4.479; Lower 95% (Parking Spaces) 4.269, Upper 95% (Parking Spaces) 15.714 e) H 0 : β 1 = β 2 = β 3 = 0 H 1 : Not all β s are 0 F Crit = 3.5874. So we reject H 0 and conclude that the linear relationship exists and at least one of the regression coefficients is not zero. 7
f) For Floor Area: For Parking Spaces: For Income: H 0 : β 1 = 0 H 0 : β 2 = 0 H 0 : β 3 = 0 H 0 : β 1 0 H 0 : β 2 0 H 0 : β 3 0 Critical t value = 2.201 (or -2.201) Floor Area and Parking Spaces, we reject the null hypothesis and keep these two variables in the model. We fail to reject the null hypothesis and discard Income as an independent variable. 4) ANOVA df SS MS F Regression 2 36020.42 18010.21 30.442 Residual (Error) 17 10057.68 591.628 Total 19 46078.10 8