x! refers to a factorial of x. Meaning, that if x = 5, then x! = 5*4*3*2*1 = 120. In Python we can use the scipy library:
from scipy.special import factorial factorial(5) > 120
X bar is a reference to the sample mean (as opposed to the population mean.)
In Python you can calculate a mean quite quickly with Numpy:
import numpy as np np.mean([1,8,20,35]) >> 16
μ (pronounced “mu” or “mew”) is the Greek letter used to reference the population mean.
A Greek Sigma of course means the SUM over a set.