  Two independent methods are employed to measure the neutrino flux of the
anti-neutrino-mode beam observed by the MiniBooNE detector. The first method
compares data to simulated event rates in a high purity $\numu$ induced
charged-current single $\pip$ (CC1$\pip$) sample while the second exploits the
difference between the angular distributions of muons created in $\numu$ and
$\numub$ charged-current quasi-elastic (CCQE) interactions. The results from
both analyses indicate the prediction of the neutrino flux component of the
pre-dominately anti-neutrino beam is over-estimated - the CC1$\pip$ analysis
indicates the predicted $\numu$ flux should be scaled by $0.76 \pm 0.11$, while
the CCQE angular fit yields $0.65 \pm 0.23$. The energy spectrum of the flux
prediction is checked by repeating the analyses in bins of reconstructed
neutrino energy, and the results show that the spectral shape is well modeled.
These analyses are a demonstration of techniques for measuring the neutrino
contamination of anti-neutrino beams observed by future non-magnetized
detectors.
