To detect small shifts in the process, two other charts have been invented: the EMWA chart (Montgomery) and the CUSUM chart
(Barnard, Schein and House).
The CUSUM chart
readily detected changes in the mean moisture content that were not detected with an X-chart.
TABLE 1 Select Capabilities of QI Macros for EXCEL * Pareto chart * Runs charts * Scatter chart * Matrix plot * Box and whisker plot * Frequency histogram * Dot plot * Multivariate plot * Cusum chart
* Control charts (13) * Control chart rules * ANOVA and statistical analysis (21) * Fill-in-the-blanks templates * Data transformation * Training and tech support
Figure 3 displays a representative CUSUM chart
, which detected the VRE outbreak early in its course.
Johnson and Bagshaw (2,9) discussed the effects of autocorrelation on the performance of the Cusum chart
The EWMA control chart differs from the similar Cusum chart
by using the additional weighting factor, which allows the adjustment of shift sensitivity.
can be used to set a "challenging but achievable" target based on the best previous actual performance.
The important thing with CUSUM charts
is not the absolute value of the CUSUM; it is the slope of the curve and any changes in this slope:
for monitoring an autocorrelated process.
In short-term trials, it may be sufficient to use Cusum charts
 (a plot against time of the daily cumulative sum of the difference between the measurement and the established mean, keeping the sign of the difference) to detect changes across time within an analytical method.
[Montgomery (1985)] on the other hand are a family of control charts based on sequential analysis methods.
The cumulative sum or CuSum charts
do not include a V-mask.