st: AW: Diffrence between sum and tabsum

 From "Martin Weiss" To Subject st: AW: Diffrence between sum and tabsum Date Tue, 15 Sep 2009 12:54:49 +0200

<>

Probably a precision issue as in

***

clear*

inp double firstweight
13949.1460454864
13949.146248765
13949.146324324
end

gen byte dummy=1

su firstweight

tab dummy,  /*
*/ sum(firstweight)

***

HTH
Martin

-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Ulrich Kohler
Gesendet: Dienstag, 15. September 2009 12:14
An: statalist
Betreff: st: Diffrence between sum and tabsum

<>

Does anybody know why -tabulate, summarize- displays a nonzero
standard-deviation for a variable that is a constant?

. tab seopsu if seopsu==948, sum(firstweight)

Cps Pr |
Sampl Un |       Summary of firstweight
5:71-73 |        Mean   Std. Dev.       Freq.
------------+------------------------------------
948 |   13949.146   .00024815           3
------------+------------------------------------
Total |   13949.146   .00024815           3

. sum firstweight if seopsu==948

Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
firstweight |         3    13949.15           0   13949.15   13949.15

. return list

scalars:
r(N) =  3
r(sum_w) =  3
r(mean) =  13949.14646024504
r(Var) =  0
r(sd) =  0
r(min) =  13949.14646024504
r(max) =  13949.14646024504
r(sum) =  41847.43938073512

. d firstweight

storage  display     value
variable name   type   format      label      variable label
----------------------------------------------------------------------------
------
firstweight     double %10.0g

. l firstweight if seopsu==948

+-----------+
| firstwe~t |
|-----------|
4256. | 13949.146 |
4365. | 13949.146 |
4537. | 13949.146 |
+-----------+

Stata/MP 11.0 for Unix (Linux 64-bit x86-64)
Born 26 Aug 2009

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/