最近在做交互效应时,发现网上有这样一个画交互作用图的方法:
rename read y
rename math x
rename socst z
generate xz=x*z
summarize z
global m=r(mean)
global sd=r(sd)
/* get range of x */
summarize x
global max = r(max)
global min = r(min)
/* recentering method */
regress y x z xz
generate zh = z - ($m + $sd)
generate xzh = x*zh
generate zl = z - ($m - $sd)
generate xzl = x*zl
regress y x zh xzh
display "equation for high z: y = 23.94895 + .6017615*x"
regress y x zl xzl
display "equation for low z: y = 28.67365 + .3595465*x"
twoway (function y = 23.94895 + .6017615*x, range($min $max)) ///
(function y = 28.67365 + .3595465*x, range($min $max)) ///
(scatter y x, msym(oh) jitter(3)), ///
legend(order(1 "z at m+1sd" 2 "z at m-1sd")) ///
ytitle(Y) xtitle(X) name(conconb, replace)
想问各位大侠的是,如果我的模型中还有其他解释变量或控制变量,而不仅仅是主效应和交互效应项,那么在诸如"equation for high z: y = 23.94895 + .6017615*x"中是否要加入其他变量?或者说不管有多少解释变量和控制变量,仅像上述那样只考虑主效应项和交互效应项的,只对其做回归,画图?
多谢了!