Add some swear words. That will make it mean. Also, add some print statements so you can see what the program is doing. And if you can not complete the problem, try it another way. Perhaps computing the mean by adding each element of the list to a total field, via a for loop. Obviously you do not understand what this code is doing so staring at it will not help; a different method may.
belowMean = alist
mean = sum(alist) / len(alist)
print "I am mean, GRRRRR", mean
print "comparing for <=", mean, "with", alist
if mean <= alist:
belowMean = item