If Kp = 0.15, which statement is true of the reaction mixture before any reaction occurs?

I believe the correct statement would be: Q>K; The reaction will proceed to the left, since Qp=1, and 1 > 0.15.

Kp is the equilibrium constant with respect to partial pressures in atmospheres.

Kp takes the same form as Kc except we use the partial pressure of gases instead of concentrations. To gauge the progress of a chemical reaction relative to equilibrium we use a quantity called the reaction quotient, Q which takes the same form as the equilibrium constant.