# Graphical Analysis

Graphing the data can be utilized for both historical data already available and when analyzing the data resulting from live data collection activities. Of course, you need to pick the right graphical tool as there are a lot of different ways to plot your data. A number of commonly used graphical tools will be covered here. However, note that if one graph fails to reveal anything useful, try another one.

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# Scatter Diagram

Many situations require the investigating whether a relationship exists between two or more variables. A line manager, for example, may want to check the relationship between the number of training hours and employee productivity, or if the number of defects is a function of the experience of the person causing it. A call center manager may be interested in studying the relationship between the number of people working on a shift and the average answer time.

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# Histograms and Box Plots

Histograms and box plots are graphical representations for the frequency of numeric data values. They aim to describe the data and explore the central tendency and variability before using advanced statistical analysis techniques. In this article, we will further discuss the similarities and differences between these two tools.

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# Process Yield Measures

An ideal process must produce without defects and without rework. To expose these unnecessary and costly inefficiencies, you should have appropriate performance metrics to measure process yield, or otherwise, the true process yield might be underestimated. Process yield measures should be able to expose even the smallest inefficiencies in a process, which will enable operations to understand their true process yield in order to set realistic improvement targets.

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# Traffic Light Assessment

Traffic Light Assessment is a rating system for evaluating the performance in relation to a goal. It is a good way to communicate performance information effectively, and have the advantage of being universally recognized by all nations. The indication of performance is done using the three colors of the real traffic lights (red, yellow and green). Good and poor performance can easily be identified, and appropriate decisions can be made to achieve the best performance.

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