The Temperature$/$Pressure correction $($PT$/$P$)$ for an ionization chamber measurement is calculated to be $1\mathrm{.}009.$

This value could represent calibration conditions at the time of measurement where:

a$.$ The chamber was placed at the wrong depth in the calibration phantom

b$.$ The temperature was less than the standard laboratory reference measurement

c$.$ The barometric pressure was less than the standard laboratory reference measurement

d$.$ There was recombination of the liberated ion pairs

e$.$ There was "stem effect" contamination from the chamber