get(L)
total = 0
n = 0
for x in L {
    total = total + x
    n = n + 1
}
n = length(L)
n = the number of numbers in L
n = the length of L

average = total / n

sum = 0
for x in L {
   sum = sum + (x - average) * (x - average)
}

answer = sum / n

answer = square root of answer
answer = sqrt (answer)