[R-meta] measurement conversion is possible ?

Martin Lobo m|obo4370 @end|ng |rom hotm@||@com
Thu Nov 7 22:54:04 CET 2019 

Thank you very much for the example. then it is impossible since the correlation between the variables is never reported. At least in the data I'm looking for. It should have a minimum correlation between the baseline variable and the varable post. is that so?

best,




Lorenzo Martín Lobo MTSAC, FACC, FESC
Especialista Jerarquizado en Cardiología
Jefe de Cardiología Hospital Militar Campo de Mayo
Ex Jefe de Unidad Coronaria Hospital Militar Campo de Mayo
Miembro Titular de la Sociedad Argentina de Cardiología
Fellow American College of Cardiology
Fellow European Society of Cardiology
Miembro del Area de Investigación de la SAC
Ex Director del Consejo de Aterosclerosis y Trombosis de la SAC
Miembro Asesor del Consejo de Aterosclerosis y Trombosis de la SAC
Ex Director del Consejo de Epidemiología y Prevención Cardiovascular de la SAC

Miembro Asesor del Consejo de Epidemiología y Prevención Cardiovascular de la SAC


Instructor de ACLS de la American Heart Association


________________________________
De: Gerta Ruecker <ruecker using imbi.uni-freiburg.de>
Enviado: jueves, 7 de noviembre de 2019 13:53
Para: Martin Lobo <mlobo4370 using hotmail.com>; Viechtbauer, Wolfgang (SP) <wolfgang.viechtbauer using maastrichtuniversity.nl>; r-sig-meta-analysis using r-project.org <r-sig-meta-analysis using r-project.org>
Asunto: Re: [R-meta] measurement conversion is possible ?


Dear Martin,


one cannot conclude from the variances of pre/post values on the variance of the pre-post difference without knowing/making assumptions about the correkation.


See the attached R code for a hypothetical example.


Best,

Gerta



Am 07.11.2019 um 16:52 schrieb Martin Lobo:
Thank you very much !!

Do you know any method to impute the standard deviation of a difference of means (that is, I have the mean 1 with its deviation and the mean 2 with its deviation, I need to estimate the deviation of m1-m2)

Best




Lorenzo Martín Lobo MTSAC, FACC, FESC
Especialista Jerarquizado en Cardiología
Jefe de Cardiología Hospital Militar Campo de Mayo
Ex Jefe de Unidad Coronaria Hospital Militar Campo de Mayo
Miembro Titular de la Sociedad Argentina de Cardiología
Fellow American College of Cardiology
Fellow European Society of Cardiology
Miembro del Area de Investigación de la SAC
Ex Director del Consejo de Aterosclerosis y Trombosis de la SAC
Miembro Asesor del Consejo de Aterosclerosis y Trombosis de la SAC
Ex Director del Consejo de Epidemiología y Prevención Cardiovascular de la SAC

Miembro Asesor del Consejo de Epidemiología y Prevención Cardiovascular de la SAC


Instructor de ACLS de la American Heart Association


________________________________
De: Gerta Ruecker <ruecker using imbi.uni-freiburg.de><mailto:ruecker using imbi.uni-freiburg.de>
Enviado: jueves, 7 de noviembre de 2019 11:41
Para: Martin Lobo <mlobo4370 using hotmail.com><mailto:mlobo4370 using hotmail.com>; Viechtbauer, Wolfgang (SP) <wolfgang.viechtbauer using maastrichtuniversity.nl><mailto:wolfgang.viechtbauer using maastrichtuniversity.nl>; r-sig-meta-analysis using r-project.org<mailto:r-sig-meta-analysis using r-project.org> <r-sig-meta-analysis using r-project.org><mailto:r-sig-meta-analysis using r-project.org>
Asunto: Re: [R-meta] measurement conversion is possible ?


Dear Martin,

There is some literature on this problem, see for example https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-135<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbmcmedresmethodol.biomedcentral.com%2Farticles%2F10.1186%2F1471-2288-14-135&data=02%7C01%7C%7C81916692f08a43a4ac7208d763a2ff2c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637087424024403615&sdata=TruzHny6sUD9ounT1LBrV0%2FuTLu7OIci8fVTp3C7SmU%3D&reserved=0>

Best,

Gerta

Am 07.11.2019 um 15:27 schrieb Martin Lobo:

Hi everyones
Several times it happens that we do not have the measure we need or its dispersion.

for example:
median (inter quartile range)
median (confidence interval)
or we have mean (standard deviation) pre test and post test, but we don't have the standard deviation of the difference.
Is there any way with this data to estimate the mean and standard deviation without too much error (or that it is accepted methodologically)?

Thank you




Lorenzo Mart�n Lobo MTSAC, FACC, FESC
Especialista Jerarquizado en Cardiolog�a
Jefe de Cardiolog�a Hospital Militar Campo de Mayo
Ex Jefe de Unidad Coronaria Hospital Militar Campo de Mayo
Miembro Titular de la Sociedad Argentina de Cardiolog�a
Fellow American College of Cardiology
Fellow European Society of Cardiology
Miembro del Area de Investigaci�n de la SAC
Ex Director del Consejo de Aterosclerosis y Trombosis de la SAC
Miembro Asesor del Consejo de Aterosclerosis y Trombosis de la SAC
Ex Director del Consejo de Epidemiolog�a y Prevenci�n Cardiovascular de la SAC

Miembro Asesor del Consejo de Epidemiolog�a y Prevenci�n Cardiovascular de la SAC


Instructor de ACLS de la American Heart Association


________________________________
e la American Heart Association

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--

Dr. rer. nat. Gerta Rücker, Dipl.-Math.

Institute of Medical Biometry and Statistics,
Faculty of Medicine and Medical Center - University of Freiburg

Stefan-Meier-Str. 26, D-79104 Freiburg, Germany

Phone:    +49/761/203-6673
Fax:      +49/761/203-6680
Mail:     ruecker using imbi.uni-freiburg.de<mailto:ruecker using imbi.uni-freiburg.de>
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--

Dr. rer. nat. Gerta Rücker, Dipl.-Math.

Institute of Medical Biometry and Statistics,
Faculty of Medicine and Medical Center - University of Freiburg

Stefan-Meier-Str. 26, D-79104 Freiburg, Germany

Phone:    +49/761/203-6673
Fax:      +49/761/203-6680
Mail:     ruecker using imbi.uni-freiburg.de<mailto:ruecker using imbi.uni-freiburg.de>
Homepage: https://www.imbi.uni-freiburg.de/persons/ruecker/person_view<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.imbi.uni-freiburg.de%2Fpersons%2Fruecker%2Fperson_view&data=02%7C01%7C%7C81916692f08a43a4ac7208d763a2ff2c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637087424024413625&sdata=3h5xgPBQ2nrdeH0OCBRn9u1IRw17YVZknO5FDKs2Xv0%3D&reserved=0>


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