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# Assymetrical confidence intervals in PHREG, how possible?

Hi all,

This afternoon I decided to plot my hazard ratio's and confidence intervals in a forest plot (horizontal bars). However, when I plot my effect sizes and confidence intervals, they are not symmmetrical (e.g. the length from the effect size to the upper and lower bound are not equal....). I have no clue how this could have happened.

I obtained by data with the PHREG procedure. The piece of syntax I used looks basically like this:

PROC PHREG data=mydata;

CLASS var1 var2 var3/ref=first;

MODEL survival*censor(0) = var1 var2 var3 / RL;

RUN;

Really hope someone can help me out!

Kind regards,

Marjolein

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Solution
‎01-02-2017 03:16 PM
Super User
Posts: 23,778

## Re: Assymetrical confidence intervals in PHREG, how possible?

I believe this is correct. Your likely plotting on a linear scale, while the model developed is an exponential model.

Answe is similar to this :

http://stats.stackexchange.com/questions/4713/binomial-confidence-interval-estimation-why-is-it-not-...

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Solution
‎01-02-2017 03:16 PM
Super User
Posts: 23,778

## Re: Assymetrical confidence intervals in PHREG, how possible?

I believe this is correct. Your likely plotting on a linear scale, while the model developed is an exponential model.

Answe is similar to this :

http://stats.stackexchange.com/questions/4713/binomial-confidence-interval-estimation-why-is-it-not-...

Contributor
Posts: 27

## Re: Assymetrical confidence intervals in PHREG, how possible?

Ah! That makes sense!!! Thank you so much. This is quite a relief

SAS Super FREQ
Posts: 4,247