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Re: st: monthly means & CI


From   Ana Gabriela Guerrero Serdan <ag_guerreroserdan@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: monthly means & CI
Date   Tue, 13 Mar 2007 11:42:59 -0700 (PDT)

Dear Nicholas, 

Thanks, yes collapse is an option but I want to
calculate means and CI for each month not for the
whole period if I use collapse then I can not use ci.
Or this  is also possible?  

I think that if I first create a unique value for each
month then I could be able to use e.g. 
by monthnumber: ci female 

so if my data looks like: 

 list month year female total

       +-------------------------------+
       | month   year   female   total |
       |-------------------------------|
    1. |     1   2006        0       1 |
    2. |     1   2006        0       1 |
    3. |     1   2004        0       1 |
    4. |     1   2006        0       1 |
    5. |     1   2006        0       1 |
       |-------------------------------|
    6. |     1   2006        0       1 |
    7. |     1   2005        0       1 |
    8. |     1   2004        0       1 |
    9. |     1   2005        0       1 |
   10. |     1   2005        0       1 |
       |-------------------------------|
   11. |     1   2006        0       1 |
   12. |     1   2005        0       1 |
   13. |     1   2006        0       1 |
   14. |     1   2004        0       1 |
   15. |     1   2006        0       1 |
       |-------------------------------|


and then I want to create a unique value for month per
year, so the new variable would take value of 1,2,3
according to the month and year. 

this is where i get stuck: 

I have tried:

1) by year month, sort: gen monthly_num=_n 

this doesnt work. 

and this
2)

. sort year month

. egen Monthly_num = group(month year)

this works but now I cannnot know which month
corresponds to the Monthly_num although I do get the
total number of monthsyear.


       +------------------------------------------+
       | month   year   female   total   Monthl~m |
       |------------------------------------------|
    1. |     3   2003        0       1          7 |
    2. |     3   2003        0       1          7 |
    3. |     3   2003        0       1          7 |
    4. |     3   2003        0       1          7 |

 

as you see the first values of Monthly_num take=7 and
should be 1. 

Anyone can help? 

thanks in advance, 





--- Clive Nicholas <crazeeclive@yahoo.co.uk> wrote:

> Gaby Serdan wrote:
> 
> I have data on deaths. I need to calculate the mean
> &
> CI of females in proportion to all population. Im
> trying first to create a variable for each month
> then
> take the total number of female per month and then
> divide by total number of deaths per month. 
> 
> [...] 
> 
> Im somehow lost, since my data is per individula.
> should I create a different dataset with montly
> deaths
> only or can I calculate means and confidence
> intervals
> in this same dataset. 
> 
>
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> 
> My suggestion would be to do the following (after
> -input-ing the data and variables that you show):
> 
> . collapse (sum) female male sex_unknown, by(month
> year)
> 
> The -count- variable seemed to me to be a bit of a
> red herring in getting what you wanted, so I
> dispensed with this. Since only one female appears
> in this snapshot of your data, I created
> the variable -prop- which records the monthly
> proportion of those who
> died where their sex is unknown.
> 
> . g total=female+male+sex_unknown
> 
> . g prop=sex_unknown/total
> 
> . sum prop, detail
> 
>                             prop
>
-------------------------------------------------------------
>       Percentiles      Smallest
>  1%          .25            .25
>  5%          .25             .5
> 10%           .5              1       Obs           
>       15
> 25%            1              1       Sum of Wgt.   
>       15
> 
> 50%            1                      Mean          
> .9166667
>                         Largest       Std. Dev.     
> .2249339
> 75%            1              1
> 90%            1              1       Variance      
> .0505952
> 95%            1              1       Skewness     
> -2.346011
> 99%            1              1       Kurtosis      
>  6.82526
> 
> . display .9166667-(.2249339*1.96)
> 
> .47579626
> 
> . display .9166667+(.2249339*1.96)
> 1.3575371
> 
> I guess you'd need to define which confidence
> interval you're looking for. The percentiles don't
> look very informative, and both subtracting and
> adding 1.96 times the standard deviation to and from
> the mean (assuming a 95% CI) gives you an upper
> confidence limit above 1, which makes little sense.
> However, applying this to all of your data might
> yield more sensible statistics.
> 
> Hope all that helps.
> 
> Clive Nicholas
> 
> 
> 
> 
> 
> 	
> 	
> 		
>
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