The SPT term (standard penetration test) and CPT term (cone penetration test) each have a set of coefficients a, b, c for a ground type and LPI giving one set of coefficients for each term in the equation. Typically, the weight is 0.333 for the CPT term and 0.667 for the SPT term. The weights must add to 1.0. If either term has coefficients of zero, the weight must be adjusted accordingly.