9.5 An in-process scale was used in preparing additives for an industrial process. The improvement team had made significant improvements in the accuracy of the scale by standardizing operations and using control charts for calibration decisions. Environmental factors (wind and temperature) were identified as possible causes of weight variations. The scale was supposed to compensate for ambient temperature fluctuations, but special causes on the control chart indicated that sometimes temperature changes appeared to have an effect.
A study was designed to evaluate the effect of wind speed and ambient temperature on scale accuracy. The accuracy was measured by loading a standard weight on the scale and recording the difference from the standard value. The team conjectured that possible interactions and nonlinear effects of these factors made it difficult to understand their effects using the control charts. A 3 × 3 factorial experiment was planned. Three levels of each factor were established from previous wind and temperature readings. The order of the tests was determined by the occurrence of the proper weather conditions. The standard weight was measured three times during each test. The following data were obtained:

Analyze the data from this study.
1. Prepare run charts of the average (to evaluate the bias of the weighing process) and the range (to evaluate the precision of the weighing process) of the scale.
2. Prepare response plots for the average and range.
3. Do either of the environmental factors affect the accuracy of the scale?
4. What additional study should be done? What are recommendations for action?

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Test Measurement-standard (lb) Test Order Wind Temperature Meas 1 Meas 2 Meas 3 1 3 Low Low 4 -.8 .6 2345 8 Low Mid -.7 .5 .3 4 Low High 2.6 3.2 2.8 6 Mid Low -1.0 .8. -.7 6 7 8 99 15279 Mid Mid -.5 1.3 .6 Mid High 3.6 2.5 3.5 High Low 2.1 -1.6 -.8. High Mid -1.3 .5 1.6 High High 1.5 4.3 2.6