104 def _sum(data, start=0):  argument
250 def _counts(data):  argument
290 def mean(data):  argument
316 def harmonic_mean(data):  argument
363 def median(data):  argument
387 def median_low(data):  argument
409 def median_high(data):  argument
428 def median_grouped(data, interval=1):  argument
483 def mode(data):  argument
525 def _ss(data, c=None):  argument
545 def variance(data, xbar=None):  argument
592 def pvariance(data, mu=None):  argument
640 def stdev(data, xbar=None):  argument
656 def pstdev(data, mu=None):  argument