Tracking error examination

When you see an error value displayed in a cell, you ll need to examine the formula. There are several things you can do to track down the error. The error value displayed can suggest a good place to begin. For example, if the error value is NAME , you most likely have misspelled a variable name or function, or entered a variable name that has not yet been defined. 

To track down the source of an error in a lengthy, complicated formula, examine the value of individual references, names, functions or function arguments. 

The previous errors addressed heterogeneity on a small scale. Now we examine heterogeneity on a large scale the scale of the lot over time or space. The long-range nonperiodic heterogeneity fluctuation error is nonrandom and results in trends or shifts in the measured characteristic of interest as we track it over time or over the extent of the lot in space. For example, measured characteristics of a chemical product may decrea.se due to catalyst deterioration. Particle size distribution may be altered due to machine wear. Samples from different parts of the lot may show trends due to lack of mixing. 

To address these limitations, Prinzel etal. (1997)conductedasecondstudy that essentially replicated the experimental condilioiis described by Pope etal. (1995) with a few differences. Fiisf they examined system operation with the indices 1/alpha, beta/alpha, and beta/(alpha + theta). Also, the system configurahon used by Prinzel et al. was similar to the one used by Pope et al. except that EEG was recorded fiom only four sites Cz, Pz, P3, and P4. In addition, they analyzed the root mean square error (RMSE) on the tracking task. 

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