Trend Chart – A line graph of data plotted over time
- Generally, 25 data points are needed to get meaningful results
- Plot the values on the chart and connect the dots.
- Calculate the median and place this on the chart. The median is the value separating the higher half of a data from the lower half.
- In the data set {1, 3, 3, 6, 7, 8, 9}, the median is 6
- In the data set (1,2,3,4,5,6, 8,9) the median is 4+5 / 2 = 4.5
Interpretation *
- 5 Points in a row rising or falling indicates a change in the process
- 6 Points in a row above or below the median also indicates a change
- Points (outliers) that appear farther away from the median than others may indicate either a change or a temporary or unusual event
- Also look for nonrandom patterns – too close or too far from the median, or cycles. The people closest to the process may be able to provide an explanation of the behavior
* Acceptable standards range anywhere from 5-8 data points. Can also just use 7.
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