The data (X1, X2, X3, X4, X5) are by city.
X1 = death rate per 1000 residents
X2 = doctor availability per 100,000 residents
X3 = hospital availability per 100,000 residents
X4 = annual per capita income in thousands of dollars
X5 = population density people per square mile
Reference: Life In America’s Small Cities, by G.S. Thomas
X6=gender where 0-male and 1-female
I need to do the analysis and do the best model
do all needed analysis such as:
-diagnostics needed
-plot the residuals
-plot the cotter plots 
– model reduction 
-Forward and backward selection 
-including the square values 
-do the validation