Dr. Jo is creating a new measure of body composition called "Ultra-CompX". This new measure uses ultrasound to show the layers under the skin including the subcutaneous fat. The depth of the subcutaneous fat (fat under the skin) is then measured at specific sites on the body (i.e., thigh, arm) and used to estimate the proportions of fat and fat-free mass.

By describing how "Ultra-CompX" works and having experts in the field agree that it is a plausible method to assess body composition, Dr. Jo is establishing which type of validity?

a) content-related validity

b) construct-related validity

c) concurrent validity

d) predictive validity