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The equation for the coefficient of correlation (r) is as follows:
r =
 
( x)( y)
xy - n
x-
x
n y-
y
n
22
 
2 2
where: n = number of observations
= sum of
Example Problems
The following example problems use data from the attached calibration worksheet.
After all the sampling site information, calibrator information, and meteorological information have been
recorded on the worksheet, standard air flows need to be determined from the orifice manometer
readings taken during the calibration using the following equation:
1. Qa = 1/m[Sqrt((H20)(Ta/Pa))-b]
where: Qa = actual flow rate as indicated by the calibrator orifice, m3/min
“H20 = orifice manometer reading during calibration, (inches) “H20
Ta = ambient temperature during calibration, K ( K = 273 + C)
Pa = ambient barometric pressure during calibration, mm Hg
m = Qactual slope of orifice calibration relationship
b = Qactual intercept of orifice calibration relationship.
Note that the ambient temperature is needed in degrees Kelvin to satisfy the Qa equation. Also, the
barometric pressure needs to be reported in millimeters of mercury. In our case the two following
conversions may be needed:
2. degrees Kelvin = [5/9 (degrees Fahrenheit - 32)] + 273
3. millimeters of mercury = 25.4(inches of H2O/13.6)
Inserting the numbers from the calibration worksheet run point number one we get:
4. Qa = 1/.99486 [Sqrt((5.45)(294/753)) - (-.00899)]
5. Qa = 1.005 [Sqrt((5.45)(.390)) + .00899]
6. Qa = 1.005 [Sqrt(2.1255) + .00899]
7. Qa = 1.005[1.4579+ .00899]
8. Qa = 1.005[1.46689]
9. Qa = 1.474
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