Why the following two formulas - with and without quotes around r() macros (see below) - produce very different results if the value stored in the r() macro is negative? I attach a part of a Stata output (Stata10SE, WindowsXP). Should not all macros, including the r() macros, be quoted?
Aleksander Rutkowski
corr empl0 empl1
local t = r(rho) * sqrt((r(N)-2)/(1-r(rho)^2))
local t2 = `r(rho)' * sqrt((`r(N)'-2)/(1-`r(rho)'^2))
local p = 2*ttail(r(N)-2,abs(`t'))
local p2 = 2*ttail(`r(N)'-2,abs(`t2'))
di "r(rho): " r(rho) " r(rho)': " `r(rho)'
di "r(N): " r(N) " r(N)': " `r(N)'
di "t: " `t' " t2: " `t2' " p: " `p' " p2: " `p2'
di
Example of Stata output:
r(rho): -.58133648 r(rho)': -.58133648
r(N): 10 r(N)': 10
t: -2.0208211 t2: -1.4215178 p: .07795928 p2: .19295556
r(rho): .85050034 r(rho)': .85050034
r(N): 10 r(N)': 10
t: 4.5735645 t2: 4.5735645 p: .00181727 p2: .00181727
r(rho): .00749718 r(rho)': .00749718
r(N): 10 r(N)': 10
t: .02120583 t2: .02120583 p: .98360083 p2: .98360083
r(rho): -.7597187 r(rho)': -.7597187
r(N): 10 r(N)': 10
t: -3.3045795 t2: -1.7110323 p: .01078497 p2: .12543946
r(rho): .18673805 r(rho)': .18673805
r(N): 10 r(N)': 10
t: .53763206 t2: .53763206 p: .60545943 p2: .60545943
r(rho): .64313145 r(rho)': .64313145
r(N): 10 r(N)': 10
t: 2.3754968 t2: 2.3754968 p: .04485987 p2: .04485987
r(rho): .74453652 r(rho)': .74453652
r(N): 10 r(N)': 10
t: 3.1544711 t2: 3.1544711 p: .01350709 p2: .01350709
r(rho): .88701037 r(rho)': .88701037
r(N): 10 r(N)': 10
t: 5.4333446 t2: 5.4333446 p: .00062087 p2: .00062087
r(rho): -.2475888 r(rho)': -.2475888
r(N): 10 r(N)': 10
t: -.72279083 t2: -.67976198 p: .49039643 p2: .51583887
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