Benefit Ratio Low

Generally, the more the variables, the greater the experimental costs and the relative value of the extra variables often diminishes. The developed model simply cannot produce valuable and tangible results in developing new drugs, new methods, or new processes with any degree of repeatability. Generally, 

It is far better to control variables—temperatore, weight, mixing, flow, drying, and so on— than to produce a model in an attempt to account for them. In practice, no quality control or assurance group is prepared to track a fourdimensional control chart, and government regulatory agencies would not support them anyway. 

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