2.2 pharmacist has been monitoring sales of a particular over-the-counter pain reliever. Daily sales during the last 15 days were; [10 marks]

Days Sales

1 81

2 86

3 95

4 99

5 108

6 110

7 113

8 110

9 117

10 108

11 117

12 124

13 122

14 126

15 128

a. Which method would you suggest using to predict future salesa linear trend equation or trend adjusted exponential smoothing? Why?

b. If you learn that the store ran out of the specific pain reliever on some days, would that knowledge cause you any concern? Explain.

c. Use exponential smoothing with a smoothing constant of 0.40 and a first-period forecast of 50 to forecast for the next period. What is the MSE for the eight forecasts for which there are actual data?