use http://www.ats.ucla.edu/stat/stata/notes/hsb2, clear

generate femXsoc=female*socst

regress write female socst femXsoc
twoway (lfit write socst if ~female)(lfit write socst if female), legend(off)
global mean = r(mean)
global sd = r(sd)

/* create new variable centered at the mean of socst */
generate mean = socst-$mean

generate femXmean=female*mean

regress write female mean femXmean


twoway (lfit write socst if ~female)(lfit write socst if female), legend(off) scheme(s2mono) xline($mean) xtitle(socst with verticle line at mean)



local classlist="josh jim tony"

foreach name in `classlist'{
	disp `name'
}

disp `classlist'





***************************************
xtile science_half = science, nq(2)


* baby question: are reading scores balanced between M/F in in the bottom half of science scores?
reg read female if science_half==1

ttest(read) if science_half==1, by(female)
if (r(p)<0.05) {
  disp "yes"
}
else {
  disp "no"
}


local joshvars read write math
foreach josh in `joshvars'{
  ttest(`josh') if science_half==1, by(female)
  if (r(p)<0.05) {
    disp "`josh': IS balanced"
  }
  else {
    disp "`josh': is NOT balanced"
  }
}



local joshvars read write math
drop count
gen count = 0
foreach josh in `joshvars'{
  ttest(`josh') if science_half==1, by(female)
  replace count = count + (r(p)<.05)
}
gen fraction = count / 3
sum fraction




ttest(write) if science_half==1, by(female)
replace count = count + (r(p)<.05)
ttest(math) if science_half==1, by(female)
replace count = count + (r(p)<.05)