st: Confidence Intervals of Predicted scores in CLARIFY - adding together

[James Laurence <james.laurence@sjc.ox.ac.uk>]

Hi there,

I was wondering if you might be able to help me with a query.

I am using the STATA program CLARIFY (Michael Tomz, Jason Wittenberg, and Gary King (2001). CLARIFY: Software for Interpreting and Presenting Statistical Results. Version 2.0 Cambridge, MA: Harvard University, June 1. http://gking.harvard.edu)

I'm using it to get a set of predicted scores from an OLOGIT model I've been running.

So, I run the model. Then...

setx mean

setx div 0.1

simqi

...this gives me a set of predicted scores for each category of my OLOGIT dependent variable:


      Quantity of Interest |     Mean       Std. Err.    [95% Conf. Interval]
---------------------------+--------------------------------------------------
            Pr(newsre~t=1) |    .025927     .0027974     .0209661    .0317577
            Pr(newsre~t=2) |   .1168595     .0059575     .1055424     .128563
            Pr(newsre~t=3) |   .6739712     .0090134     .6563168    .6909184
            Pr(newsre~t=4) |   .1832423     .0074309     .1699783    .1987786

I want to create a graph in excel using the top two categories combined: so 0.674 + 0.183 = this gives me a predicted score of 0.86

Here's  my question. I also want to add CONFIDENCE INTERVALS to this value using the C.I.s provided by CLARIFY. Do I simply add the C.I.'s together for the top two categories as I did with the predicted scores? 
e.g. the C.I.s for this predicted score would be min. 0.656 + 0.169  and the max. would be 0.691 + 0.199?

So, the C.I.s of my predicted score of 0.86 (minimum  0.825) and (maximum 0.888)? 

Is this correct?

Thanks in advance

James

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