CV = (sigma/x-bar) * 100% is a dimensionless measure of relative variability. It allows comparison between datasets with different units or different scales. Lower CV indicates more consistency. Example: if heights have mean 170 cm with SD 10 cm (CV=5.9%) and weights have mean 70 kg with SD 8 kg (CV=11.4%), heights are relatively less variable. JEE may ask which dataset is "more consistent" — always compare CV, not SD directly. CV is undefined if mean is zero.