BOOKS OF RtfiDIfGS - PAHO/WHO

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of (0.02 x 0.065/0.30) x 100 = 0.43% in maximum average occupancy. SIMULATION
OF HOSPITAL
Similarly, for percent EMG (Fig. 3b, 40 beds), an error of 2 percent in OCCUPANCY
percent emergency would cause the following error in maximum
average occupancy for the 30 and 50 percent emergency levels:
(0.02 x (0.937 - 0.897)/0.20) x 100 = 0.40%
These figures represent the maximum errors in occupancy. In general
(at different parameter levels) the error will be much smaller because
the differences in the numerator are smaller. The possible errors are
easily calculated from the graphs for an individual case. (It is interesting
that the error increases as the number of beds decreases.)
As with any simulation, there is a certain variability in results
due to pseudorandom generation of numbers. In order to estimate
the variance in occupancy within the simulation, 20 100-week runs
were performed with identical inputs but with different seeds for the
random number generators. The sample standard deviation in mean
percent occupancy between runs was found to be 0.033 percent.
It is possible to estimate the total error in predicted maximum
average occupancy due to the simulation. Assuming that the error
due to pseudorandom number generation is normally distributed
and using a 99-percent confidence interval, the maximum error in
occupancy (percent) is
2.58 x (o-EM 2 + arEL 2 + 'RNp2) X 100
where oE, = the standard deviation of the error due to variation
in percent emergency. The maximum error is already
computed as 0.43 percent. Assuming thie error to be
normally distributed and using 99-percent confidence
intervals
YO -EM 0.43/(2.58 x 100) = 0.00167
oEL = the standard deviation due to variation in percent electives.
The maximum error is computed as 0.40 electives.
Using the same assumptions'as for o'Em
EZL f 0.40/(2.58 X 100) --'0.00155
CraN = the standard deviation due to pseudorandom number
generation. This has previously been found to be
0.00033. Therefore, maximum error in occupancy =
±2.58 x (0.001672 + 0.001552 + 0.000332)J x 100 = +0.594
percent occupancy. This figure, ±0.594 percent occupancy,
is an estimate of the maximum error due to the
sources discussed above.
Restu. . FALL.
1978
The results of the procedures outlined are shown in Figs. 2-5,
and the effects of the different parameters on occupancy are discussed