In biofiltration of wastewater, air discharged from a treatment facility is passed through a damp porous membrane that causes contaminants to dissolve in water and be transformed into harmless products. The accompanying data on x inlet temperature (°C) and y removal efficiency (%)

was the basis for a scatter plot that appeared in the article

“Treatment of Mixed Hydrogen Sulfide and Organic Vapors in a Rock Medium Biofilter”(Water Environment Research, 2001: 426–435).

Calculated summary quantities are , and gy . i 2 5 309,892.6548 gxi y gxi i 5 37,850.7762 3149.04, 2 5 5099.2412, gxi 5 384.26, gyi 5

a. Does a scatter plot of the data suggest appropriateness of the simple linear regression model?

b. Fit the simple linear regression model, obtain a point prediction of removal efficiency when temperature 10.50, and calculate the value of the corresponding residual.

c. Roughly what is the size of a typical deviation of points in the scatter plot from the least squares line?

d. What proportion of observed variation in removal efficiency can be attributed to the model relationship?

e. Estimate the slope coefficient in a way that conveys information about reliability and precision, and interpret your estimate.

f. Personal communication with the authors of the article revealed that there was one additional observation that was not included in their scatter plot: (6.53, 96.55). What impact does this additional observation have on the equation of the least squares line and the values of s and r2 ?