[ncl-talk] confidence interval on a regression line
debasish mazumder
debasish at ucar.edu
Tue May 5 11:57:27 MDT 2015
Hi All,
I am trying to plot confidence interval on a regression line (like
attached image)
I have x and y two variables.
x varies between -0.07 and 0.06
y varies between -0.8 and 0.5
I followed following steps:
step 1: rc = regline (x,y)
step 2: yReg = rc*x + rc at yintercept ; regression line
step 3: /a = rc at rstd/ * 2.048 ; where /t/ for 0.975 and 28 degrees of
freedom is 2.048 [table look-up].
step 4: confidence interval rc1 = rc+a and rc2 = rc-a
step 5: confidence interval around regression line
yReg_1 = rc1*x + rc at yintercept
yReg_2 = rc2*x + rc at yintercept
But I am not getting the expected plot. Moreover yReg_1 and yReg_2
intersect each other.
Could you please point out what I am doing wrong.
with regards
-Debasish
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