The article “Chemithermomechanical Pulp from Mixed High Density Hardwoods” (TAPPI, July 1988: 145–146) reports on a study in which the accompanying data was obtained to relate y = specific surface area (cm2/g) to x1 = % NaOH used as a pretreatment chemical and x2 = treatment time (min) for a batch of pulp.
*1 | X2 | y |
3 | 30 | 5.95 |
3 | 60 | 5.60 |
3 | 90 | 5.44 |
9 | 30 | 6.22 |
9 | 60 | 5.85 |
9 | 90 | 5.61 |
15 | 30 | 8.36 |
15 | 60 | 7.30 |
15 | 90 | 6.43 |
The accompanying Minitab output resulted from a request to fit the model
a. What proportion of observed variation in specific surface area can be explained by the model relationship?
b. Does the chosen model appear to specify a useful relationship between the dependent variable and the predictors?
c. Provided that % NaOH remains in the model, would you suggest that the predictor treatment time be eliminated?
d. Calculate a 95% CI for the expected change in specific surface area associated with an increase of 1% in NaOH when treatment time is held fixed.
e. Minitab reported that the estimated standard deviation
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Chapter 13 Solutions
Probability and Statistics for Engineering and the Sciences
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