Random assignment of treatment and control using else condition

Question

I am trying to learn else condition loops in Stata. To do this I'm trying random assignment into treatment and control. However, I keep getting the error: '{' invalid

I can do it normally:

g treat = 0 if random > 0.5 
replace treat = 1 if random < 0.5

However, I want to try it out with the else condition. Moreover, additional resources to learn the if condition would also be greatly appreciated. The else condition loop that I am trying:

clear all
// Set the seed for the random number generator
set seed 98034

set obs 10000
// Generate 1000 random numbers between 0 and 1
g random = runiform()

// For each observation, assign it to the treatment group if the random number is less than 0.5, and to the control group otherwise

forvalues i = 1(1)10000 {
    g treatment = 1 if random[`i'] < 0.5 {
        else {
            treatment[`i'] = 0
        }
    }
}

Answer 1

While gen treatment = runiform() < 0.5 generates two identically sized groups on average, it is not guaranteed that the groups are the same size. Therefore, I think random assignment should be done by random ranking.

clear all
// Set the seed for the random number generator
set seed 98034
set obs 10000
// Assign treatment using 1000 random numbers between 0 and 1
gen  rand = runiform() 
sort rand
gen treatment = (_n <= _N/2)
tab treatment

Technically, to make the randomization truly reproducible you also need to set the Stata version (for example, version 16) and stably sort the data (for example isid idvar, sort) before using runiform().