where X = the array of values 



X = the arithmetic mean of the X array 



n = the number of elements in the X array 



o = the standard deviation 



Subroutine AMEAN is called to compute the arithmetic mean of the X 

 array . 



Subroutine TINORM computes the value of the inverse of the normal 

 distribution by a rational approximation. The inverse normal distribution 

 is defined by the solution for X of the following integral equation 





"t Z /2 .«. 

 e dt = a 



where a is the probability for which the ordinate is to be calculated. 

 The rational approximation itself may be ascertained from the FORTRAN 

 statements in the subroutine. 



3. Input-Output Subroutines 



The binary input-output statements in FORTRAN, although conven- 

 ient to use, cannot make efficient use of magnetic tapes because the 

 language does not permit total parallel processing. Furthermore, a 

 considerable amount of time is used in processing a list because of its 

 generality. More efficient use is attained by buffering the input or 

 output in parallel with computing. On the UNIVAC 1108 system the NTRAN 

 subroutine provides a means of buffering through a call statement in 

 FORTRAN : 



CALL NTRAN (UNIT, sequence of operations) 



in which UNIT is an integer constant or variable designating the logical 

 unit. If the unit is not busy, NTRAN initiates the first operation and 

 stacks the remainder in a waiting list. If the unit is already busy, 

 then the entire sequence is stacked in a waiting list and chained to the 

 previously stacked sequence. Control is then returned to the program 

 following the call NTRAN statement. When an interrupt occurs, NTRAN 

 records the transmission status, initiates the next operation in the 

 chain and returns control to the interrupted program. 



The NTRAN subroutine is used to write out on magnetic tape the 

 arrays containing the legend, sequence number, underwater detector co- 

 ordinates and corrected count rate for both radiation channels for each 

 file of survey data being processed. The information thus stored on 



