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## 6.5.3 Understanding the Trends view 

In the Trends view (Figure 6-14), the frequency of the selected time period is shown as a bar chart. It is scaled accordingly from 0 to the maximum frequency count along the vertical y-axis on the left side. 

On the right side of the y-axis is a scale that represents the increase indicator. The increase indicator , also known as trend index, is a scale to measure the increase ratio of the frequency for a given time interval as compared to the expected average frequency that is calculated based on the changes in the past time interval frequencies. This expected change in frequency is estimated by using a modified Poisson distribution. The increase indicator is shown as a blue line graph in the chart, as shown in Figure 6-14. 

The bar chart is in color (to highlight) whether the increase indicator is higher than what was expected within reasonable limits. This result means that the actual value is greater than the estimated value by a certain amount. Figure 6-14 shows a brighter orange color for December 2008. As you can see from the blue line in the graph, the increase indicator shows a sudden jump, which means that you might want to conduct additional investigation and analysis for that time period. 

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