Summarizing Data

It seems that as often as we sort data, we summarize data. For example, my monthly mobile phone bill lists the total number of phone calls that I made and the total number of airtime minutes that I used. These data values are also subtotaled by daytime, nighttime, and weekend airtime minutes. As another example, the daily stock report usually provides the opening, closing, highest, and lowest price of various financial markets, among other summary values.

From a business point of view, summarizing data reduces the amount of detailed data you need to review. This allows you to

• Make comparisons to other data over time more easily. For instance, if you are comparing sales profits over two years’ time, reviewing a group of monthly or quarterly data values is probably easier than looking at daily or weekly data values.

• Make data trending tasks easier. Using the previous example, stating sales profits by quarter or month is less time-consuming than stating sales profits by week or day.

The data analysis tools described in this book support summarization, but this technique is not a part of all the features in the applications. For example, Access supports summarization in data forms, queries, and reports, but it does not support summarization in data tables.

Your Turn

This exercise demonstrates how you can use summarized data to make quick observations about a set of data.

1. In the CustServ.xls file (located in the Chap02 folder), examine the data on the Original Data worksheet. This data describes a restaurant’s average monthly customer service ratings in several measurement areas, from 1 (poor) to 5 (excellent).

2. Now examine the summarizations on the Summarized by Year worksheet, shown in Figure 2-3.

   
   Figure 2-3.: Data summarized by year.

After just a few seconds, you can make a couple of observations about the three years’ worth of customer service scores:

• Wait times received the lowest scores, while servers received the highest scores.

• Hosts and cashiers received about the same scores.

Summarizations enable you to make observations about large sets of data faster.