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Re: st: Cox proportional hazard model


From   Nyasha Tirivayi <ntirivayi@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Cox proportional hazard model
Date   Fri, 13 Aug 2010 01:00:05 +0200

Dear Michael and Maarten

I guess I got confused because I read the following manual from page 13.

http://rikain.com/Manuals/Social_+_Human_Rights/practical-guide-%20to-transition-data-analysis.pdf

And in it the writer acknowledged they did not actual data on
employment and unemployment spells. So they created spells where the
first spell was from time AIDS medicaiton began to first survey.
Second spell was time from first survey to second survey.

If you have time, please kindly browse through the manual and kindly
confirm if it is in error!

Regards

Nyasha Tirivayi
Maastricht University

On Fri, Aug 13, 2010 at 12:39 AM, Nyasha Tirivayi <ntirivayi@gmail.com> wrote:
> Dear Michael
>
> Thanks for the suggestion. I will change my approach.
>
> Nyasha Tirivayi
> Maastricht University
>
> On Fri, Aug 13, 2010 at 12:34 AM, Michael McCulloch
> <mm@pinestreetfoundation.org> wrote:
>> Nyasha, Maarten explained very well the nature of what data you'd need to to
>> time-to-employment analysis, which it turns out you can't measure in the
>> context of your current project. This means you can't do survival analysis
>> like the Cox method.
>>
>> Another alternative analysis strategy is to instead study the likelihood of
>> a person getting a job within some pre-determined time frame, using logistic
>> regression. The dependent variable then is getting employment (yes/no), and
>> the predictor variables are things like
>>                food aid
>>                use of AIDS medication
>>                and other characteristics of the person or household
>> Michael
>>
>>
>> On Aug 12, 2010, at 3:06 PM, Nyasha Tirivayi wrote:
>>
>>> Dear Maarten
>>>
>>> Thanks for clarifying. Now I understand. I had this wrong. In that
>>> case I think I need to ask for ideas for alternative method since I do
>>> not have data on employment/unemployment spells.
>>>
>>> I have realized that I have 2 period panel data on employment status.
>>> So I have employment1 and employment2. I am interested in seeing the
>>> effects of AIDS medication  on transitions from one state to another.
>>>
>>> I also have another treatment variable- food aid. So you have some
>>> households where a patient is on AIDS medication and household
>>> receives food assistance. If I choose instead to look at the effect of
>>> food assistance ( meaning all households in analysis will now have a
>>> patient on AIDS medication), what kind of transition analysis can I
>>> do.. or maybe I should simply carry out multiple regression analysis
>>> or propensity score matching?
>>>
>>> Kindly advise
>>>
>>> Regards
>>>
>>> Nyasha Tirivayi
>>> Maastricht University
>>>
>>> On Thu, Aug 12, 2010 at 11:56 PM, Maarten buis <maartenbuis@yahoo.co.uk>
>>> wrote:
>>>>
>>>> --- On Thu, 12/8/10, Nyasha Tirivayi wrote:
>>>>>
>>>>> So the duration of the AIDS medication taken by the patient
>>>>> is the time variable, and getting employed/returning to work
>>>>> is the event
>>>>
>>>> The time variable and the event are not two separate concepts,
>>>> the duration is the time till the event occurs. When you look
>>>> at time till employment, then starting AIDS medication is not
>>>> the beginning of a spell, leaving the labor market, leaving
>>>> school, becoming unemployed, are the beginning of the spell.
>>>> Whether or not the patient takes AIDS medication is your
>>>> explanatory variable, not your explained variable.
>>>>
>>>> Hope this helps,
>>>> Maarten
>>>>
>>>> --------------------------
>>>> Maarten L. Buis
>>>> Institut fuer Soziologie
>>>> Universitaet Tuebingen
>>>> Wilhelmstrasse 36
>>>> 72074 Tuebingen
>>>> Germany
>>>>
>>>> http://www.maartenbuis.nl
>>>> --------------------------
>>>>
>>>>
>>>>
>>>>
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>>>
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>>
>>
>> Best wishes,
>>
>> Michael McCulloch, LAc MPH PhD
>> Pine Street Foundation
>> 124 Pine Street
>> San Anselmo, CA 94960-2674
>> tel:    415-407-1357
>> fax:    206-338-2391
>>
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>>
>

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