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Re: st: Change of reference group in linear multiple regression analysis
From
Nick Cox <[email protected]>
To
[email protected]
Subject
Re: st: Change of reference group in linear multiple regression analysis
Date
Thu, 9 Aug 2012 15:49:01 +0100
No magic. You pick one out of the air with a bit of guesswork. In this
case, I assume that some residents could have immigrated ~100 years
ago, but skewness implies that a midpoint near 70 would be quite
wrong. If the guesswork looks crucial, a little sensitivity analysis
is called for.
I don't think literature references are always needed. If you think
something is a good idea, do it and publish it.
Nick
On Thu, Aug 9, 2012 at 4:39 PM, Richard Williams
<[email protected]> wrote:
> At 08:38 AM 8/9/2012, Nick Cox wrote:
>>
>> Why not -recode- to say 1, 4, 8, 15, 25, 40 and use the quantitative
>> information you have? Sure, there is some arbitrariness involved, but
>> it is defensible.
>
>
> I've done this myself. But does anybody know of any literature that defends
> (or attacks) the practice? It seems like the most difficult part is the
> open-ended upper category -- how should you choose a value for that?
>
>> Nick
>>
>> On Thu, Aug 9, 2012 at 2:30 PM, Richard Goldstein
>> <[email protected]> wrote:
>>
>> > I assume you are using an up-to-date version of Stata; see -h fvvarlist-
>> > and look under "base level"
>>
>> On 8/9/12 9:25 AM, Amal Khanolkar wrote:
>>
>> >> Hi, I'm currently running a linear multiple regression analysis where
>> >> the principle explanatory variable is:
>> >>
>> >> Years since |
>> >> immigration | Freq. Percent Cum.
>> >> ------------+-----------------------------------
>> >> <3 yrs | 106,794 3.57 3.57
>> >> 3-5 yrs | 91,311 3.05 6.62
>> >> 6-10 yrs | 96,657 3.23 9.85
>> >> 11-19 yrs | 82,344 2.75 12.61
>> >> 20-29 yrs | 50,954 1.70 14.31
>> >> >=30 yrs | 2,563,396 85.69 100.00
>> >> ------------+-----------------------------------
>> >> Total | 2,991,456 100.00
>> >>
>> >> - Currently the default group is the first category, <3yrs. I would
>> >> however like to change this in the regression to the last group >=30 years.
>> >> How do I do this without having to recode the above variable?
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