arr = [1.339333765, 1.28025286, 1.349310146, 1.379461397, 1.290007132]
arrAvg = 1.32767306

sum = 0.0

for i in range(0, 5):
    sum += (arr[i] - arrAvg)**2 / (5 * (5 - 1))
    print(i, ") ", (arr[i] - arrAvg)**2 / (5 * (5 - 1)))

print("Sx = ", sum)
print("Δɣ = ", 1.32767306, "±", 2.77 * sum)