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# st: Diffrence between sum and tabsum

 From Ulrich Kohler To statalist Subject st: Diffrence between sum and tabsum Date Tue, 15 Sep 2009 12:14:10 +0200

```<>

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 |
+-----------+

. about

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```

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