Clausen's theorem and hypergeometric functions over finite fields

We prove a general identity for a 3F2 hypergeometric function over a finite field Fq, where q is a power of an odd prime. A special case of this identity was proved by Greene and Stanton in 1986. As an application, we prove a finite field analogue of Clausen’s Theorem expressing a 3F2 as the square of a 2F1. As another application, we evaluate an infinite family of 3F2(z) over Fq at z = −1/8. This extends a result of Ono, who evaluated one of these 3F2(−1/8) in 1998, using elliptic curves.