Run Chart

Constructing Run Charts

A run chart is a line graph that shows data points plotted in the order in which they occur. They are used to show trends and shifts in a process over time, variation over time, or to identify decline or improvement in a process over time. They can be used to examine both variables and attribute data.

Steps in Constructing a Run Chart

1. Draw and label the vertical (y) axis using the measurement units you are tracking (e.g., numbers of defectives, mean diameter, number of graduates, percent defective, etc.)
2. Draw and label the horizontal (x) axis to reflect the sequence in which the data points are collected (e.g., week 1, week 2, ... or 8AM, 9AM, 10AM, etc.)
3. Plot the data points on the chart in the order in which they became available and connect the points with lines between them.
4. Calculate the average from the data, and draw a horizontal line across the chart at the level of the average.
5. Interpret the chart and decide what action to take. Are trends present? Would the chart look different if everything were perfect? The key is to look for trends, and not focus on individual points.

Example:

Average Math Entrance Exam Scores by Year                       
                                
        Average 
Year  Math Score        
1975    139
1976    130
1977     61     
1978    164             
1979    129
1980    100
1981    108             
1982    110     
1983     68             
1984     78     
1985     57     
1986     77     
1987     38             
1988     53             
1989     50     
1990     81             
1991    105             
1992     65             
1993     97             
1994     62             
1995     96
1996     93             

Run - Chart:

It should be obvious from this chart, that average math scores in the eighties dropped from those in the seventies, and now, in the nineties have rebounded somewhat but are still lower than they were in the seventies.