* normal distribution curve used in Solution 1 of Example 5.4.1
clear
set obs 401
gen x = -20 + 40/400*(_n-1)
gen pdf = normalden(x/7.3)
gen x_axis = 0
label variable pdf "Probability Density"
twoway (line pdf x, sort) (line x_axis x, sort)

* normal distribution curve used in Solution 2 of Examples 5.4.1 and 5.4.2
clear
set obs 401
gen z = -4 + 8/400*(_n-1)
gen pdf = normalden(z)
gen z_axis = 0
label variable pdf "Probability Density"
twoway (line pdf z, sort) (line z_axis z, sort)

* normal distribution curve used in Solution 1 of Example 5.4.2
clear
set obs 401
gen x = 0 + 30/400*(_n-1)
gen pdf = normalden((x-15)/4.0532)
gen x_axis = 0
label variable pdf "Probability Density"
twoway (line pdf x, sort) (line x_axis x, sort)