*! version 1.0.1   12 September 1993   RG                STB-17: sg21.1
program define equipi
    version 3.1
* this is the version that formed the examples in the STB
* enter control group first: p n pbase [d1] [d2] or p1 n1 p2 n2 d1 [d2]
    local options "Delta(string) SDelta(string)"
    parse "`*'", parse(" ,")
    tempname pr1 n1 pr2 n2 d1 d2
    scalar `pr1'=`1'
    scalar `n1'=`2'
    scalar `pr2'=`3'
    capture confirm integer number `4'
    if _rc!=0 {
         mac shift 3
         parse "`*'"
         if "`delta'"=="" { scalar `d1'=.2*`pr2' }
         else if "`delta'"!="" {
              if substr("`delta'",-1,.)=="%" {
                   local leng=length("`delta'")
                   local dp=real(substr("`delta'",1,`leng'-1))/100
                   scalar `d1'=`dp'*`pr2'
              }
              else { scalar `d1'=real("`delta'") }
         }
         if "`sdelta'"=="" { scalar `d2'=`d1' }
         else if substr("`sdelta'",-1,.)=="%" {
              local leng2=length("`sdelta'")
              local dp2=real(substr("`sdelta'",1,`leng2'-1))/100
              scalar `d2'=`dp2'*`pr2'
         }
         else { scalar `d2'=real("`sdelta'") }
         local sep=sqrt(((`pr1'*(1-`pr1'))/`n1'))
         local p1= ((`pr1' - `pr2') - (-`d1'))/ `sep'
         local p2= ((`pr1' - `pr2') - `d2')/ `sep'
         local CI1 = (`pr1' - `pr2')-(invnorm(.95)*`sep')
         local CI2 = (`pr1' - `pr2')+(invnorm(.95)*`sep')
         local succ=round(`pr1'*`n1',1)
         qui cii `n1' `succ', level(90)
         local eci1=round($S_5,.00001)
         local eci2=round($S_6,.00001)
         qui bitesti `n1' `succ' `pr2'
         local ep1=round($S_1,.00001)
         local ep2=round($S_2,.00001)
         di "Westlake version of test of Equivalence:"
         di "   test1: "%9.3f `p1' _skip(3) "p-value: "%6.4f /*
              */ round(1-normprob(`p1'),.0001) _skip(13) /*
              */ "exact p-value: "%6.4f `ep1'
         di "   test2: "%9.3f `p2' _skip(3) "p-value: "%6.4f /*
              */ round(normprob(`p2'),.0001) _skip(13) /*
              */ "exact p-value: "%6.4f `ep2'
         di "  Confidence Interval: Lower Limit"%11.5f `CI1' _skip(5) /*
              */ "Upper Limit "%11.5f `CI2'
         di "  Exact Westlake CI: Lower Limit"_skip(2) %11.5f `eci1' _skip(5) /*
              */ "Upper Limit "%11.5f `eci2'
         di "Equivalence Interval (-/+ (s)delta): "%8.5f (`pr2' - `d1') /*
              */ _skip(17) %11.5f (`pr2' + `d2')
         di ""
         qui bitesti `n1' `succ' `pr2'
         local pv=round($S_7,.00001)
         di "Exact p-value from binomial test for single proportion: "%8.5f `pv'
         qui cii `n1' `succ'
         local lci=round($S_5,.00001)
         local uci=round($S_6,.00001)
         di "Exact CI: Lower Limit "_skip(12) %11.5f `lci' _skip(5) /*
              */ "Upper Limit "%11.5f `uci'
         local tCI1 = (`pr1' - `pr2')-(invnorm(.975)*`sep')
         local tCI2 = (`pr1' - `pr2')+(invnorm(.975)*`sep')
         di "Traditional CI: Lower Limit "_skip(6) %11.5f `tCI1' _skip(5) /*
              */ "Upper Limit "%11.5f `tCI2'
         exit
    }
    scalar `n2'=`4'
    mac shift 4
    parse "`*'"
    if "`delta'"=="" { scalar `d1'=.2*`pr1' }
    else if "`delta'"!="" {
         if substr("`delta'",-1,.)=="%" {
              local leng=length("`delta'")
              local dp=real(substr("`delta'",1,`leng'-1))/100
              scalar `d1'=`dp'*`pr1'
         }
         else { scalar `d1'=real("`delta'") }
    }
    if "`sdelta'"=="" { scalar `d2'=`d1' }
    else if substr("`sdelta'",-1,.)=="%" {
         local leng2=length("`sdelta'")
         local dp2=real(substr("`sdelta'",1,`leng2'-1))/100
         scalar `d2'=`dp2'*`pr1'
    }
    else { scalar `d2'=real("`sdelta'") }
    local se1 = sqrt(((`pr1'*(1-`pr1'))/`n1')+((`pr2'*(1-`pr2'))/`n2'))
    local p1= ((`pr1' - `pr2') - (-`d1'))/ `se1'
    local p2= ((`pr1' - `pr2') - `d2')/ `se1'
    local CI1 = (`pr1' - `pr2')-(invnorm(.95)*`se1')
    local CI2 = (`pr1' - `pr2')+(invnorm(.95)*`se1')
    di "Westlake version of test of Equivalence:"
    di "   test1: "%9.3f `p1' _skip(3) "p-value: "%6.4f /*
         */ round(1-normprob(`p1'),.0001)
    di "   test2: "%9.3f `p2' _skip(3) "p-value: "%6.4f /*
         */ round(normprob(`p2'),.0001)
    di "  Confidence Interval: Lower Limit"%11.5f `CI1' _skip(5) /*
    */ "Upper Limit "%11.5f `CI2'
    di "Equivalence Interval (-/+ (s)delta): "%8.5f (- `d1') /*
         */ _skip(17) %11.5f (`d2')
    di ""
    di "standard test for comparing proportions: "
    local av=(`pr1'+`pr2')/2
    local z= (`pr1'-`pr2')/sqrt(`av'*(1-`av')*((1/`n1')+(1/`n2')))
    di "    z = "%9.3f `z' _skip(5) "p-value: "%7.4f 1-normprob(abs(`z'))
    local CIp1=(`pr1'-`pr2')+(invnorm(.025)*`se1')
    local CIp2=(`pr1'-`pr2')+(invnorm(.975)*`se1')
    di "confidence interval: Lower Limit "_skip(1) %11.5f `CIp1' _skip(5) /*
         */ "Upper Limit "%11.5f `CIp2'
end