Youden Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Youden and links to relevant pages within the course.
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|What is a Levey-Jennings Chart?|
The Levey-Jennings chart usually has the days of the month plotted on the X-axis and the control observations plotted on the Y-axis. On the right is the Gaussian or "bell-shaped" curve turned on its side to show the correlation of the curve to the chart (ie, fewer data points should appear on the upper and lower extremities of the chart, since the "bell" is thinner farther from the mean). By observing the data plotted in the L-J chart, we can determine if test results are in control and accurate, or if test results are not in control and consequently unacceptable. Use of the Westgard, Cumulative Summation Rules, and the Youden plots will help establish an effective error-detecting scheme.
|What is a Youden Plot?|
In the late 1950's, Dr. William Youden (1900-1971) developed what has now become known as the Youden Plots. This statistical technique involves both normal and abnormal controls and graphically helps to differentiate between systematic and random errors. The inner square of the plot (yellow) represents one standard deviation (1SD). The next larger square (green) represents 2SD, and the outer square (blue) represents 3SD. A horizontal median line is drawn parallel to the X-axis and a second median line is drawn parallel to the Y-axis. The intersection of the two median lines is called the Manhattan Median. One or two 45-degree lines are drawn through the Manhattan Median. The results of at least two different levels of controls (e.g. Level 1/Level 2 or Normal/Abnormal) are then plotted on the chart as X-axis versus Y-axis.
|Using a Youden Plot|
Controls are run and plotted. Plots that lie near the 45-degree reference line and within the one and two standard deviation squares show acceptable results. Points that lie near the 45-degree reference lines but outside the 2SD square indicate a systematic error. Points that lie far from ether 45-degree reference line indicate a random error.
|Examining the Youden Plot to the right, you would:||View Page|
|In the accompanying Youden plot, what conclusions can be drawn about the data?||View Page|