Date:         Wed, 20 Jun 2001 18:40:31 -0300
Reply-To:     Hector Maletta <hmaletta@OVERNET.COM.AR>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Hector Maletta <hmaletta@OVERNET.COM.AR>
Subject:      Re: Analyses of Weighted Data in SPSS - Explanation
Comments: To: Shail Dobson <dobson_shail@HOTMAIL.COM>
Content-Type: text/plain; charset=us-ascii

I knew that SPSS rounds (up or down) any weighted frequencies that have
a fractional part, which only happens if the weights themselves are not
integers (and this is a good reason to avoid fractional weights). This
could cause rounding differences or errors for the same total obtained
in different statistical procedures (e.g. in DIFFERENT tables involving
different variables). But I cannot fathom why the rounding is different
for two procedures that should theoretically yield the same result (as
in the SAME table produced by CROSSTABS or TABLES).

Hector Maletta
Universidad del Salvador
Buenos Aires, Argentina

Shail Dobson wrote:
>
> Sorry I did not give enough information about my observation. Here are some
> details to my earlier e-mail:
>
> Version: SPSS 10.1 for windows
> Data: weighed data
>
> Here are syntax:
>
> WEIGHT
>   BY weight variable.
>
> For Crosstabs:
> CROSSTABS
>   /TABLES= childbirth  BY county
>   /FORMAT= AVALUE TABLES
>   /CELLS= COUNT ROW .
>
> For Custom Table:
> * Basic Tables.
> TABLES
>   /FORMAT BLANK MISSING('.')
>   /TABLES childbirth
>   BY country > (STATISTICS)
>   /STATISTICS
>   count( ( F5.0 ))
>   cpct( ( PCT5.1 ) 'Row %':country ).
>
> My purpose was to do a crosstab between variable childbirth and country. I
> found that the Crosstabs (in Descriptive Statistics) output numbers are
> slightly different than those produced through in Custom Tables.
>
> There is a great likelihood that I am missing something.... I really would
> like to know the reason why numbers are different in these setting if
> weighted data is used.
>
> >-----Original Message-----
> >From: Shail Dobson [mailto:dobson_shail@HOTMAIL.COM]
> >Sent: Wednesday, June 20, 2001 12:35 PM
> >To: SPSSX-L@LISTSERV.UGA.EDU
> >Subject: Analyses of Weighted Data in SPSS
> >
> >
> >Hello!
> >
> >While analysing weighted data, I made the following observation, hoping you
> >may find it useful.
> >
> >If you have weighted data, Crosstabs under Descriptive Statistics DO NOT
> >give the accurate numbers because the Crosstabs option does not take into
> >account the decimal places (it simply round up the number to zero decimal);
> >however, the Customer Tables option produced the more accurate number
> >because it do includes decimals places.
> >
> >I wonder why SPSS do that?!
>
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