1. Prepare a graph of the data. On this same graph, plot a12-month moving average forecast. Discuss any apparent trend and seasonal patterns.
2. Use regression to develop a trend line that could be used to forecast monthly sales for the next year. Is the slope of this line consistent with what you observed in question 1? If not, discuss a possible explanation.
3. Use the multiplicative decomposition model on these data. Use this model to forecast sales for each month of the next year. Discuss why the slope of the trend equation with this model is so different from that of the trend equation in question 2.
Monthly Revenue (in $1,000s)
MONTH 2008 2009 2010
January 438 444 450
February 420 425 438
March 414 423 434
April 318 331 338
May 306 318 331
June 240 245 254
July 240 255 264
August 216 223 231
September 198 210 224
October 225 233 243
November 270 278 289
December 315 322 335