Question 737:

Asked on May 31, 2009

Tags: Time-Series

1

Answer:

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1. Q737_1_timeSeriesQ737.xls

a. The MILK CATEGORY was chosen.
b. The data have been plotted in Minitab and MegaStat  (see the attached excel file with graph) and we see a rather steady downward trend in the data--meaning milk consumption is waning (going down).  A likely cause is the more recent discussion in the media regarding milk's association with more fat and calories and not necessary in lunch-rooms.
c. A fitted trend is helpful in confirming the downward trend we see in the datapoints.
d. I used MegaStat and fit a Linear and two log trends. The Linear model fits best as it had the highest R-Squared value of .982 vs. the log trends of .976.
e. In using the linear trend model we can use the regression equation to predict the value for 2005 by inserting it in the regression equation. I used MegaStat and selected t=6 as the prediction and got 20.08 as the best predicted value for mill consumption in 2005.