Statistics for Environmental Engineers

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Box, G. E. P. and G. C. Tiao (1975.). “Intervention Analysis with Applications to Economic and Environmental Problems,” J. Am. Stat. Assoc., 70, 70-79.


Pallesen, L., P. M. Berthouex, and K. Booman (1985). “Environmental Intervention Analysis: Wisconsin’s Ban on Phosphate Detergents,” Water Res., 19, 353-362.

Exercises


54.1 White Noise Process. The data below represent 20 weekly averages before a change in polymer in a treatment process, and 20 weekly averages following the intervention. Time runs from left to right. Estimate the magnitude and 95% confidence interval of the intervention due to the polymer change.


Pre-interventionPolymer A


58


75


77


75


61


91


64


79


82


74


73


72


85


61


52


77


59


72


62


79


Post-


intervention


Polymer B


87


88


87


80


71


74


69


91


92


83


102


45


90


65


82


95


67


75


88


81

54.2 Random Walk Model. The data below represent 20 hourly readings before an intervention occurred in a random walk process, and 20 hourly readings following the intervention. Time runs left to right. Estimate the magnitude and 95% confidence interval of the intervention.


Pre-intervention


10.7 10.9 11.2


10.5


9.7


9.0


8.9


9.6


9.0

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