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st: highly skewed, highly zeroed data


From   "Jason Ferris" <JasonF@TURNINGPOINT.ORG.AU>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: highly skewed, highly zeroed data
Date   Wed, 25 Nov 2009 13:07:28 +1100

Hi, 
I have tried to find my answer in the statalist repository but nothing
has quite hit the mark.

I would like to calculate a mean and 95% CI of this data - which is
highly skewed and the majority are zeros.

I am aware of adding a constant and the transforming on the log scale
(with antilog) for interpretation.  However after adding a constant to
overcome the zero issue and then transforming on the log scale I am
still left with a highly skewed distribution.  Which gets me no close to
a mean and CI.

PS. As this is survey data I would be most keen for the 'right' answer
to be addressed in svy: terms

Jason

 time (hrs) |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        518       80.06       80.06
        .25 |          2        0.31       80.37
         .5 |          3        0.46       80.83
          1 |         15        2.32       83.15
        1.5 |          1        0.15       83.31
          2 |         23        3.55       86.86
          3 |         10        1.55       88.41
        3.5 |          1        0.15       88.56
          4 |         11        1.70       90.26
          5 |         13        2.01       92.27
          6 |          9        1.39       93.66
          7 |          3        0.46       94.13
          8 |         19        2.94       97.06
         20 |         10        1.55       98.61
         45 |          9        1.39      100.00
------------+-----------------------------------

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