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CAPINTEC, INC. CAPTUS
®
3000
CHI-SQUARE TEST
CAUTION: Calibration is recommended before making any measurements. Refer to
the
AUTO CALIBRATION section on page 5-5.
The Chi-Square Test provides a sensitive check of the overall counting performance of the
system. The software will use the 662 keV peak of your Cs137 source for the tests.
# Repetitions 0.95 0.90 0.10 0.05
5 .711 1.06 7.78 9.49
10 3.33 4.17 14.7 16.9
15 6.57 7.79 21.1 23.7
20 10.1 11.7 27.2 30.1
In the table above, you can see that for a typical 10-repetition test, the Chi-Square value
should be between 3.33 and 16.9 for 95% of the time. Therefore, it is expected to be outside
this range 5% of the time. Also, because of the statistical nature of the Chi-Squared test, the
Chi-Square values should not remain exactly the same. They are expected to vary.
The Chi-Squared test value is calculated from the following equation:
( )
∑
=
− =
n
i
av i
av
x x
x
1
2
2
1
χ
ts measuremen for the average
t measuremen for counts where
n x
i x
av
i
=
=
This equation is the same as the following:
( ) ( ) ( )
{ }
2 2
2
2
1
2
...
1
av n av av
av
x x x x x x
x
− + + − + − =
χ
1. Click the button or press Alt+H on Figure 5-1 Quality Assurance
Main Screen. The screen appears as shown in Figure 5-16 Chi-Square Test Screen.
July 14 QUALITY ASSURANCE 5-15