The classified department of a monthly magazine has used a combination of quantitative and qualitative methods to forecast sales of advertising space. Results over a 20-month period are as follows:

Month	Error	Month	Error
1	-8	11	1
2	-2	12	6
3	3	13	9
4	8	14	2
5	10	15	2
6	4	16	-2
7	1	17	-6
8	-5	18	-7
9	-10	19	-5
10	-3	20	-1

Click here for the Excel Data File

a. Compute a tracking signal for months 11 through 20. To do so, compute an initial value of MAD for month 11, and then update it for each month using exponential smoothing with = .2. (Leave no cells blank - be certain to enter "0" wherever required. Negative values should be indicated by a minus sign. Round your intermediate calculations and final answers to 3 decimal places.)

b-1. Using the first half of the data, construct a control chart with 2s limits. (Round your intermediate calculations to 3 decimal places and final answer to 2 decimal places.)

b-2. What can you conclude? multiple choice

All errors are within these limits.

Only the error for month 9 is outside of the limits.

Only the error for month 5 is outside of the limits.