R help - Jul 2011 - Meta-analysis with zero values for mean and sd

Hi!
I want to do a meta-analysis with count data for treatement/control cases.
Mi problem is that I need to use zero values (an informative value) for the
mean and standard deviation for one of the treatement, but R has a
problem: "Studies
with zero values for sd.e or sd.c get no weight in meta-analysis". I can
agroup the case by Family (byvar=Family).
¿anybody help me? Thanks!

>
datos<-read.table(file="datos_totales.csv",head=TRUE,sep=",",dec=",")
> datos[10:20,]
            Study ControlN ControlMean ControlSD TreatedN TreatedMean
TreatedSD       Family
10 Ali.Gmb.S1.Inv        3    893.3333 180.36999        3  1213.33333
410.52812 Capitellidae
11 Ali.Gmb.S2.Inv        3    640.0000 348.71192        3   666.66667
220.30282 Capitellidae
12 Ali.Gmb.S3.Inv        3    426.6667 184.75209        3   920.00000
628.64935 Capitellidae
13 Ali.Cul.S1.Ver        3    213.3333 115.47005        3     0.00000
0.00000 Cirratulidae
14 Ali.Cul.S2.Ver        3    160.0000 144.22205        3    40.00000
 40.00000 Cirratulidae
15 Ali.Cul.S3.Ver        3    293.3333 234.37861        3    26.66667
 46.18802 Cirratulidae
16 Ali.Cul.S1.Inv        3    653.3333 532.66625        3    13.33333
 23.09401 Cirratulidae
17 Ali.Cul.S2.Inv        3    706.6667 335.45988        3    26.66667
 23.09401 Cirratulidae
18 Ali.Cul.S3.Inv        3    666.6667 674.48746        3    80.00000
 80.00000 Cirratulidae
19 Ali.Gmb.S1.Ver        3    280.0000  69.28203        3     0.00000
0.00000 Cirratulidae
20 Ali.Gmb.S2.Ver        3    226.6667 220.30282        3     0.00000
0.00000 Cirratulidae
>  library(meta)
>
 metaanalisis2<-metacont(TreatedN,TreatedMean,TreatedSD,ControlN,ControlMean,ControlSD,data=datos,byvar=Family,label.c="Control",print.byvar=FALSE,label.e="Treatment",studlab=Study)
Mensajes de aviso perdidos
In metacont(TreatedN, TreatedMean, TreatedSD, ControlN, ControlMean,  :
  Studies with zero values for sd.e or sd.c get no weight in meta-analysis

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On 07/09/2011 08:16 PM, Rosana Ferrero wrote:
> Hi!
> I want to do a meta-analysis with count data for treatement/control cases.
> Mi problem is that I need to use zero values (an informative value) for the
> mean and standard deviation for one of the treatement, but R has a
> problem: "Studies
> with zero values for sd.e or sd.c get no weight in meta-analysis". I
can
> agroup the case by Family (byvar=Family).
Hi Rosana,
Your data indicates that in three studies, whatever was being measured 
had a value of zero for each of the three spaghetti worms in the 
treatment group. Maybe they were dead or something. You may be able to 
get away with substituting a very small value (0.1 or something) for the 
SD in these cases. However, I would look very carefully at what this 
means. If, say, the worms are dead, is the measurement between live and 
dead worms meaningful? Just a guess.

Jim