def prob_drunk_given_positive(prob_drunk_prior=0.001, prob_positive=0.08,prob_positive_drunk=1.0):
	"""
	Returns the Bayesian probability that a person is drunk,
	given a positive result in a breathalyzer test

	Arguments:
		prob_drunk_prior (float, optional, default: 0.001): Probability that a person in the prior population is drunk
		prob_positive (float, optional, default: 0.08): Probability a breathalyzer gives a false positive
		prob_positive_drunk (float, optional, default: 1.0): Probability a breathalyzer gives a true positive

	Returns:
		(float): Probability a person is drunk, given a positive breathalyzer result
	"""

	return(prob_positive_drunk * prob_drunk_prior / 
		(prob_positive_drunk*prob_drunk_prior + prob_positive*(1-prob_drunk_prior)))