* To learn more about aweight
* https://www.stata.com/support/faqs/statistics/analytical-weights-with-linear-regression/

u NHIS2009_clean, clear

* Without aweight
sort hi
ttest hlth if fml==0, by(hi)

* Question a 

* Comparison of husband health by health insurance outcome

* Use summing and by hand with equal variances 

sum hlth if fml==0 & hi==1 [ w=perweight ] 
local N1 = r(N)
local av1 = r(mean)
local sd1 = r(sd)

sum hlth if fml==0 & hi==0 [ w=perweight ] 
local N2 = r(N)
local av2 = r(mean)
local sd2 = r(sd)

ttesti `N1' `av1' `sd1' `N2' `av2' `sd2' , level (95)

* Use summing and by hand with unequal variances 
sum hlth if fml==0 & hi==1 [ w=perweight ] 
local N1 = r(N)
local av1 = r(mean)
local sd1 = r(sd)

sum hlth if fml==0 & hi==0 [ w=perweight ] 
local N2 = r(N)
local av2 = r(mean)
local sd2 = r(sd)

ttesti `N1' `av1' `sd1' `N2' `av2' `sd2' , unequal


* Question b

* i.	are employed?

* Use summing and by hand with equal variances 

sum hlth if fml==0 & hi==1 &  empl==1 [ w=perweight ] 
local N1 = r(N)
local av1 = r(mean)
local sd1 = r(sd)

sum hlth if fml==0 & hi==0 &  empl==1 [ w=perweight ] 
local N2 = r(N)
local av2 = r(mean)
local sd2 = r(sd)

ttesti `N1' `av1' `sd1' `N2' `av2' `sd2' , level (95)


* ii.	are employed and have at least 12 years of education?

* Use summing and by hand with equal variances 

sum hlth if fml==0 & hi==1 &  empl==1 & yedu>=12 [ w=perweight ] 
local N1 = r(N)
local av1 = r(mean)
local sd1 = r(sd)

sum hlth if fml==0 & hi==0 &  empl==1 & yedu>=12  [ w=perweight ] 
local N2 = r(N)
local av2 = r(mean)
local sd2 = r(sd)

ttesti `N1' `av1' `sd1' `N2' `av2' `sd2' , level (95)

* iii.	are employed, have at least 12 years of education, and earn income of at least $80,000? 

sum hlth if fml==0 & hi==1 &  empl==1 & yedu>=12 & inc>=80000 [ w=perweight ] 
local N1 = r(N)
local av1 = r(mean)
local sd1 = r(sd)

sum hlth if fml==0 & hi==0 &  empl==1 & yedu>=12 & inc>=80000 [ w=perweight ] 
local N2 = r(N)
local av2 = r(mean)
local sd2 = r(sd)

ttesti `N1' `av1' `sd1' `N2' `av2' `sd2' , level (95)


* Question c
*by regression 
reg hlth hi if fml==0 [ w=perweight ], robust
eststo m1 

reg hlth hi age if fml==0 [ w=perweight ], robust
eststo m2 

reg hlth hi age yedu if fml==0 [ w=perweight ], robust
eststo m3 

reg hlth hi age yedu inc if fml==0 [ w=perweight ], robust
eststo m4 

#d;
esttab m1 m2 m3 m4 using table1nhis.rtf, replace
cells(b (star fmt(3)) se(par fmt(2)))
varlabels(health "Health"
      hi "Health insurance"
	  empl "Employed dummy"
	  inc "Income"
	  yedu "Years of Education"
	  _cons "Constant")
nomtitle title("Table 1")
label
stats(r2 N rmse,  fmt(4 0 4) labels("R squared" "No. of obs." "Root Mean Square Error"))
starlevels(* 0.10 ** 0.05 *** 0.01)
collabels(none) stardetach legend
note ("Robust standard errors in parenthesis.")
;