Final answer:
BIA measures body fat percentage using electrical conductivity, but its accuracy compared to criterion methods varies. Criterion methods like DEXA and the skin-fold test provide more accurate measurements.
Step-by-step explanation:
Bioelectric Impedance Analysis (BIA) measures body fat percentage by passing a small amount of electricity through the body and analyzing the rate at which it travels.
Although BIA devices are commonly used, their theoretical accuracy compared to criterion methods varies.
Dual-energy X-ray absorptiometry (DEXA) is a criterion method used to measure body fat percentage accurately by directing low-dose X-ray beams through the body.
Another commonly used criterion method is the skin-fold test, where a caliper measures the thickness of skin on different body parts.