Interarrival Statistics for Time Sharing Systems
The optimization of time-shared system performance
requires the description of the stochastic 
processes governing the user inputs and the program activity.
 This paper provides a statistical description 
of the user input process in the SDC-ARPA general-purpose
Time-Sharing System (TSS).  The input process 
is assumed to be stationary, and to be defined by the
interarrival time distribution.  The data obtained 
appear to justify satisfactorily the common assumption
that the interarrival times are serially independent. 
 The data do not appear to justify, except as a very
rough approximation, the usual assumption off an 
exponential distribution for interarrival time.  A much
more satisfactory approximation to the data can 
be obtained with a biphase or triphase hyperexponential distribution.
CACM July, 1966
Coffman, E. G.
Wood, R. C.
