The heights 145, 150, 155, 160 and 165 cm occur with frequencies 6, 4, 10, 12 and 8. Using the assumed mean A = 155, find the mean height in cm.

With $d=x-155$ the deviations are −10, −5, 0, 5, 10 and Σ$fd=6(-10)+4(-5)+10(0)+12(5)+8(10)=-60-20+0+60+80=60$. Since Σ$f=40$, the mean is 155 + 60/40 = 156.5 cm. Stopping at the assumed mean (155) or subtracting the correction (153.5) are the usual slips.