Data Analysis with Microsoft Excel: Updated for Office 2007

Chapter 11 Times Series 467

The plot shows that production is seasonal, with peaks occurring each winter

(around the holidays). There also appears to be another peak in the summer,

perhaps around the fourth of July. In addition to the seasonality of the data,

there appears to be a linear trend of increasing sales from 1996 to 2007.

Examining Seasonality with a Boxplot

One way to see the seasonal variation is to make a boxplot, with a box for

each of the 12 months. This gives you a picture of the month-to-month vari-

ation in liquor sales. The shape of each box tells you how production for

that month varied from 1996 to 2007.

To create the boxplot:

1 Click the Liquor Sales sheet tab.

2 Click Single Variable Charts from the StatPlus menu and click

Boxplots.

3 Click the Connect Medians between Boxes checkbox.

4 Click the Data Values button and select Sales from the range names

list. Click OK.

Figure 11-24
Liquor sales from
1996 to 2007