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We present a measurement of the mass difference Δmd for the B0 meson and the statistical power of the b flavor tagging methods used. The measurement uses 90 pb-1 of data from pp̅ collisions at √s =1.8 TeV collected with the CDF detector. An inclusive lepton trigger is used to collect a large sample of B hadron semileptonic decays. The mass difference Δmd is determined from the proper time dependence of the fraction of B hadrons that undergo flavor oscillations. The flavor at decay is inferred from the charge of the lepton from semileptonic B decay. The initial flavor is inferred by determining the flavor of the other B hadron produced in the collision, either from its semileptonic decay (soft-lepton tag) or from its jet charge. The measurement yields Δmd=(0.500±0.052±0.043)h\ ps-1, where the first uncertainty is statistical and the second uncertainty is systematic. The statistical powers (εD2) of the soft-lepton and jet-charge flavor taggers are (0.91±0.10 ±0.11)% and (0.78±0.12±0.08)%, respectively.