Re: st: SE and CI by mrtab

[Steve Samuels <sjsamuels@gmail.com>]

Each "percentage" has the form P = (mentions of category X)/(number of mentions).  Numerator and denominator are random for each person, so the percentages are actually
ratios:

******************************
 use http://fmwww.bc.edu/RePEc/bocode/d/drugs.dta, clear
 mrtab inco1-inco7, include title(Sources of income) width(24)
 egen sumi = rowtotal(inco*)
 ratio inco1/sumi
*****************************

Since Abu is knowledgeable about SPSS, I'd appreciate a reference to the confidence interval formulas that SPSS uses when percentages add to more than 100%.  (I couldn't find one in the SPSS 16 algorithms manual.)  I'd appreciate it also if he would compare the calculation above to the one that SPSS reports.

Steve
sjsamuels@gmail.com


On May 14, 2012, at 8:40 AM, Nick Cox wrote:

If a program is counting mentions, they are not people. Either way, I stand by what I said. I don't think even "sample size" is well defined for such data, so I don't see how inference is well defined. 

I can't comment on what SPSS does, but I repeat my request. I would be grateful for literature references showing that SPSS, or anybody else, really has a solution for this problem. Just counting mentions regardless of where they come from sounds somewhere between dubious and fallacious to me. 

The author of -mrtab- is Ben Jann, who is not a member of Statalist. If you want his answers, you need to write to him directly. 

Nick 
n.j.cox@durham.ac.uk 

Abu Camara

Thanks Nick. Consider the table below and you want to get the "se"
& "ci"for the responses variable which are in percentages. I was able
to do this for
other survey questions which are not multiple responses. Perhaps the
author might consider
including standard errors & confidence interval generation in his
program. I will have to turn to
SPSS which has the facility.

--------------------------------------------------------------------------------------------------------.

mrtab inco1-inco7, include title(Sources of income) width(24)

Pct. of     Pct. of
Sources of income       Freq.   responses       cases
-------------------------------+-----------------------------------
inco1          private support         226       12.83       23.25
(partner, family,
friends)
inco2           public support         607       34.47       62.45
(unemployment insurance,
social benefits)
inco3             drug dealing         293       16.64       30.14
inco4    housebreaking, theft,          50        2.84        5.14
robbery
inco5             prostitution          82        4.66        8.44
inco6       "mischeln"/begging         151        8.57       15.53
inco7         legal occupation         352       19.99       36.21
-------------------------------+-----------------------------------
Total        1761      100.00      181.17


On 14 May 2012 14:35, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> I don't really have further comments. I was half-assuming that you know exactly what you seek, but if so you are not spelling it out.
> 
> As I see it, you would need to specify what data generation process you expect to apply and e.g. how confidence intervals are to be defined and calculated.
> 
> For example, if the question is mode of transport to work and the answers look like
> 
> Car
> Car, train, walk
> Walk
> Yak
> Horse
> Camel
> Personal helicopter
> ...
> 
> it is not clear to me what meaning there could be to a standard error around the percent of people who say "walk". If the principle is that people can specify a variety of answers, the associated data generation process seems elusive to me. You can always count "mentions" rather than "people" but the inference for that I don't think is obvious.
> 
> So, I don't think you can blame Stata for neglecting this area unless you can point to literature in which the logic is explained.
> 
> Nick
> n.j.cox@durham.ac.uk
> 
> Abu Camara
> 
> Hi Nick,
> 
> Thanks for the reply.
> I have no idea of writing my own program for "mrtab" to compute "se" &
> "ci". Further help/suggestion would be appreciated.
> Official Stata appears to be weak in complex tabulation.
> Abu.
> 
> On 14 May 2012 12:18, Nick Cox <njcoxstata@gmail.com> wrote:
>> SJ-5-1  st0082  . . . . . . . . . . . . . . . Tabulation of multiple responses
>>        (help _mrsvmat, mrgraph, mrtab if installed)  . . . . . . . .  B. Jann
>>        Q1/05   SJ 5(1):92--122
>>        introduces new commands for the computation of one- and
>>        two-way tables of multiple responses
>> 
>> You are correct, I think. -mrtab- doesn't provide these, so you may
>> need to write your own program.
>> 
>> Nick
>> 
>> On Mon, May 14, 2012 at 10:09 AM, Abu Camara <abucamara@gmail.com> wrote:
>> 
>>> I am running one and two way tables of multiple response using the
>>> user-written command "mrtab" (Stata 11.2). I tried to generate both
>>> standard errors and
>>> confidence intervals for tables of percentages but I could not find
>>> this as an option.

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