/********************* cars97a.sps **********************/
set width=80 length=none.
title 'Car data: Quant-Cat interaction'.
data list file = 'cars.dat' free / country mpg weight length.
value labels  country    1 'USA'  2 'Japan'  3 'Other'.

recode country (missing=sysmis) (1=1) (else=0) into c1.
recode country (missing=sysmis) (3=1) (else=0) into c2.
/* This makes Japan the comparison group.
compute cw1 = c1* weight.
compute cw2 = c2* weight.

/* First look at country uncorrected for weight
oneway mpg, weight by country(1,3) / statistics=descriptives
       / ranges = tukey.

regression variables = weight mpg c1 to cw2
           / statistics = defaults change
           / dependent = mpg
           / enter weight
           / enter c1 c2  /* Country controlling for weight
           / enter cw1 cw2. /* Weight by country interaction