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L1592_frame_C28.fm Page 259 Tuesday, December 18, 2001 2:48 PM

28.5 Water Pipe Corrosion. Environmental engineering students at Tufts University performed a
4−1
2 fractional factorial experiment to investigate the concentration of iron in drinking water
in various campus buildings as a means of inferring water pipe corrosion. The four experimental
factors were age of building, building type, location, and day of week. Estimate the main and
interaction effects and their 95% confidence intervals. The design identity is I == == 1234, and the
results are:

Age Type Location Day Iron (mg/L)
Old Academic Medford Wednesday 0.26, 0.21
New Academic Medford Monday 0.37, 0.32
Old Residential Medford Monday 0.01, 0.05
New Residential Medford Wednesday 0.03, 0.07
Old Academic Somerville Monday 0.11, 0.05
New Academic Somerville Wednesday 0.06, 0.03
Old Residential Somerville Wednesday 0.03, 0.05
New Residential Somerville Monday 0.07, 0.02

© 2002 By CRC Press LLC