Corrections applied to statistical programs contained in two subroutines of the Bed Rest Analysis Software System (BRASS) are summarized. Two subroutines independently calculate significant values within the BRASS program

Brand, S. N.

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Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=19850017810 2020-03-20T19:36:15+00:00Z
TECHNICAL INFORMATION RELEASE C-1
ITIR	 2114-MED-5007
TO
Joel	 I.	 Leonard, Ph.D. N.	 Cintron,	 Ph.D./SD4
DATE CONTRACT NO: T.O.OR A.D. REF: IS OR OTHER NASA REF:
4/8/85 NAS9-17151
SUBJECT
Alterations/Corrections to the BRASS Program
(NASA-C8-171874)	 AKTE6AT:	 NE /COPPECTIONS	 TO	 N85-26121
THE	 BRASS FHOGFA@	 (Canagement and Technical
Services	 Cc.)	 j	 F	 LC	 A02/NF	 A01 CSCI 06S
Uncla:
G3/52	 21221
This report briefly summarizes corrections
applied to statistical
	 programs contained
in two subroutines of the Bed Rest Analysis
Software System.
Susan N. Brand
Attachment
/db
Unit	 Approving	 NASA
Manager	 Manager	 F. A. Kutyn
	
Ph.11oncurrence,_
DISTRIBUTION
	
NASA/JSC: MATSCO:
	 GE:
Billy J. Jefferson/BE3 R. F. Meyer
	 T. Gregory/Contracts
P. Johnson/SD3 BRAP Group
	 Contracts File
J.	 Charles/SD3 TIR files
M.	 Bungo/SD3
J. Logan/SD2
V. Schneider/SD3
W. Shumate/SA
J. Vanderploeg/SB
i
1
iAlterations/Corrections to the BRASS Program
The Bed Rest Analysis Software System (BRASS) contains a data base of
experimental results from a number of bed rest studies conducted over a
10-year period at the U.S. Public Health Hospital in San Francisco. It also
includes subsystem programs which facilitate data analyses and displays.
While conducting bed-rest data analyses with the BRASS program during the last
contract period (1980-82), which led to the publication of the "Report of the
Bed-Rest Data Analysis. Treatment: Bed Rest Only" (TIR 2114-MED-2021), an
inconsistency in the calculation of significance (t-statistic) values was
revealed.
Two subroutines, the LOOK and STAT subroutines, independently calculate
i
significance values within the BRASS program. The significance values
calculated by the STAT subroutine were tested extensively and found to be
is
correct (with one exception discussed later), however, many of the values 	 Z
calculated by the LOOK subroutine were erroneously small (i.e., erroneously 	 i
significant). The t-statistic computations in the LOOK and STAT subroutines 	 1
were identical, however, the LOOK subroutine received erroneous input data for 	 9
one of its variables. In STAT, the variables S1 and S2 were the sums of the 	
(!
squares of their values from their respective means for populations 1 and 2.
In LOOK, these same variables (S1 and S2) were the standard deviations of the
populations; that is, the sum of squares divided by their degrees of freedom.,.
To correct this problem an array, designed for storage and retrieval of the
sum of squares data, was incorporated into the BRASS program and applied to
the t-statistic variables in the LOOK subroutine.
The above modification to the BRASS program corrected most of the 	 i
erroneous significance values calculated by the LOOK subroutine; however,
incorrect values were also encountered in both the STAT and LOOK subroutine
for tests in which the s'iandard deviations of both sample populations were
equal to zero. These errors were the source of round-off errors and were
corrected by checking for standard deviations less than lx!' , ^ -7 . Previously
the standard deviation was checked for values equal to zero.
i
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Akterations/corrections to the BRASS Program

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