A subset of Statistical Process Control (SPC) methodology known as Control Charting is introduced. SPC methodology is a collection of graphical and inferential statistics techniques used to study the progress of phenomena over time. The types of control charts covered are the null X (mean), R (Range), X (individual observations), MR (moving…

The agreement between visual analysis and the results of the split-middle method of trend estimation was examined using a set of 24 stimulus graphs and 30 raters. Results revealed poor agreement between the two methods, and low sensitivity, specificity, and predictive ability for visual analysis in relation to statistical inferences. (JDD)