Page 173 - Six Sigma Demystified

154 Six SigMa DemystifieD

a. Column a contains a set of uniform distributed random variables be-
tween 0 and 1.
b. Column B contains the time between order arrivals, calculated using an
exponential distribution at the specified arrival rate applied to the uniform
distributed data of column a. For example, if the average time between
order arrivals is 60 minutes (i.e., one order per hour), then row 2 of column
B contains the expression “=60*(-LN($a2)).”
c. Column C contains the order arrival time, expressed in minutes since
the start of the eight- hour work day. Row 2 contains the value “0”; row 3
contains the expression “=iF(C2+B3>480,0,C2+B3).” an order received
after the end of the business day (time exceeding 480 minutes) is as-
signed a value zero, indicating the first order to process the following
day.
d. Column D contains the order arrival day. Row 2 contains the value “1”;
row 3 contains the expression “=iF(C3=0,D2+1,D2).”
e. Column E contains the order start time, expressed in minutes since the
start of the eight- hour workday. Row 2 contains the expression “=iF(K2>
K1,0,iF(K2>D2,J1,iF(C2>J1,C2,J1)))” based on the following logic:
(1) if the order is processed on the arrival day and arrives after the
prior order was completed, then the arrival time is the start time; if the
prior order is still in progress, the order is started once the prior order is
completed.
(2) if this order is the first order for the next day (based on comparison of
the current and prior values in column K), its start time is 0; if it is processed
the day after it arrives (based on comparison of columns D and K) but is not
the first order, its start time is the end time of the last order; otherwise, its
start time is the prior order completion time.

f. Column F contains the number of line items (random numbers based
on a Poisson distribution).
g. Column g contains another set of uniformly distributed random vari-
ables between 0 and 1.
h. Column H contains the call arrival rate (calls per hour), calculated with
an exponential distribution. if the call arrival rate is 3, then row 2 contains
the expression “ =3*(-LN(g2)).”
i. Column i contains the order process time, calculated using the regres-
sion equation from the designed experiment, based on the call arrival rate
and the number of line items.