### Authors

Photios
G. Ioannou
& Julio C. Martinez

Civil & Environmental Engineering Department

University of Michigan

Ann Arbor, Michigan 48109-2125, U.S.A.

e-mail: photios@umich.edu

### Abstract

The comparison of alternative construction methods is one of the principal
reasons for using simulation to model construction processes. The efficiency and
effectiveness of such comparisons can be greatly improved by the prudent use of
"*matched pairs*", a variance
reduction technique based on dedicated and fully synchronized random number
streams. The basic methodology is illustrated by using the Stroboscope
simulation system to compare two alternative construction methods for rock
tunneling (*Conventional vs. the New Austrian Tunneling
Method*). For this example the effects are dramatic. The probability
of identifying and choosing the cheaper construction method based on a single
run increases from 55% to 96%, the variance of the cost difference decreases by
two orders of magnitude, and the 95% confidence interval for the true cost
difference given by 4,000 independent runs can be obtained by performing only 7
replications using matched pairs. Besides this improvement in statistical
efficiency, the use of matched pairs is a necessity for this example in order to
compare the alternatives on a logical and equitable basis..

### Keywords

STROBOSCOPE, construction, simulation, modeling, tunneling, NATM, variance
reduction, random number streams, common random numbers, design of experiments,
comparison of alternatives.

### Availability

Ioannou, P.G., J.C. Martinez, "Comparison of Construction
Alternatives Using Matched Simulation Experiments," *Journal of
Construction Engineering and Management, ASCE*, Vol. 122, No. 3, 231-241,
September 1996.

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This page last updated 02/16/18
, by P.G. Ioannou