Model 1a: ARG_i = b₁ + b₂ AGEDIFF_i + e_i

where ARG_i = average weekly number of arguments between heterosexual couple i

      AGEDIFF_i = absolute difference in age between members of couple i

Model 1b: ARG_i = b₁ + b₂ AGEDIFF_i + b₃ AGEMALE_i + e_i

 where AGEMALE_i = age of the male partner in heterosexual couple i

 Model 1c: ARG_i = b₁ + b₂ AGEDIFF_i + b₃ AGEMALE_i + b₄ AGEFEM_i + e_i

 where AGEFEM_i = age of the female partner in heterosexual couple i

CAUTION: Model 1c will fail if the male is always older than the female in your sample. Why?

Model 2a: TRIPS_i = b₁ + b₂ DIST_i + e_i

where TRIPS_i = number of recreational trips to Lake Wobegon by person i

      DIST_i = distance from home to Lake Wobegon for person i

Model 2b: TRIPS_i = b₁ + b₂ DIST_i + b₃ AGE_i + e_i

 where AGE_i = age of person i

 Model 2c: TRIPS_i = b₁ + b₂ DIST_i + b₃ AGE_i + b₄ BOATS_i + e_i

 where BOATS_i = number of boats owned by person i

Model 2d: TRIPS_i = b₁ + b₂ DIST_i + b₃ AGE_i + b₄ BOATS_i + b₅ KIDS_i + e_i

 where KIDS_i = number of children in the household of person i