%macro boot( B , data = x1 ) ;
data x1 ;
    set samp( keep = weight height obs = 50 ) ;
run ;
data x2 ;
    set samp( keep = weight height obs = 100 firstobs = 51 ) ;
run ;
data boot&data ;
    keep b1 Sxy Sxx ;
    do i = 1 to &b ;
        x = 0 ;
        y = 0 ;
        xx = 0 ;
        yy = 0 ;
        xy = 0 ;
        do n = 1 to nobs ;
            k = ceil( ranuni( 0 ) * nobs ) ;
            set &data  nobs = nobs point = k ;
            x = x + height ;
            y = y + weight ;
            xx = xx + height ** 2 ;
            yy = yy + weight ** 2 ;
            xy = xy + height * weight ;
            if n = 50 then
                do ;
                    CFxy = x * y  / n ;
                    CFx  = x ** 2 / n ;
                    Sxy  = xy - CFxy  ;
                    Sxx  = xx - CFx   ;
                    b1   = Sxy / Sxx  ;
                    b1   = round( b1, .01 ) ;
                end ;
        end ;
        output ;
    end ;
    stop ;
run ;
%mend boot ;