'Create a new EWMA with a specific smoothing constant.
:type period: C{int}
:param period: the time in minutes it takes to reach a given significance level
:type interval: C{int}
:param interval: the expected tick interval, defaults to 5s'

def __init__(self, period, interval=INTERVAL, clock=time):

    super(ExpWeightedMovingAvg, self).__init__()
    self.clock = clock
    self.uncounted = 0.0
    self.interval = interval
    self.rate = (-1)
    self.period = (period * ExpWeightedMovingAvg.SECONDS_PER_MINUTE)
    self.last_tick = self.clock.time()
