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<p>Dear Martin,</p>
<p><br>
</p>
<p>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.</p>
<p><br>
</p>
<p>See the attached R code for a hypothetical example.</p>
<p><br>
</p>
<p>Best,</p>
<p>Gerta<br>
</p>
<p><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">Am 07.11.2019 um 16:52 schrieb Martin
Lobo:<br>
</div>
<blockquote type="cite"
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Thank you very much !!</div>
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<br>
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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)<br>
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<br>
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Best</div>
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<br>
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<font face="Courier New"><b><i><span
style="line-height:16.05px; color:rgb(38,114,236)"><font
size="5">Lorenzo Martín Lobo </font></span></i></b></font><font
face="Courier New"><b><i><sup><span
style="line-height:13.375px;
color:rgb(38,114,236)"><font size="1">MTSAC, FACC,
FESC</font></span></sup></i></b></font><br>
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<font style="font-size:12pt"><i style="font-size:12pt"><font
face="Garamond"><b>Especialista Jerarquizado en
Cardiología</b></font></i></font></div>
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face="Garamond"><b><font
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font-style:normal; font-weight:400;
background-color:rgb(255,255,255); font-size:12pt"><i><font
face="Garamond"><b>Jefe de Cardiología </b></font></i></font><i
style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt"><font
face="Garamond"><b>Hospital Militar Campo de
Mayo</b></font></i><br>
</b></font></i></font></div>
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<font style="font-size:12pt"><i style="font-size:12pt"><font
face="Garamond"><b>Ex Jefe de Unidad Coronaria </b></font></i></font><i
style="font-size:12pt; font-variant-ligatures:inherit;
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face="Garamond"><b>Hospital Militar Campo de Mayo</b></font></i></div>
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<div style="display:inline!important"><i
style="font-size:12pt"><font face="Garamond"><b>Miembro
Titular de la Sociedad Argentina de Cardiología</b></font></i></div>
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<font style="font-size:12pt"><i style="font-size:12pt">
<div style="display:inline!important"><i
style="font-size:12pt"><font face="Garamond"><b>Fellow
American College of Cardiology</b></font></i></div>
</i></font></div>
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<font style="font-size:12pt"><i style="font-size:12pt">
<div style="display:inline!important"><i
style="font-size:12pt"><font face="Garamond"><b>Fellow
European Society of Cardiology</b></font></i></div>
</i></font></div>
<div style="color:rgb(33,33,33);
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<font style="font-size:12pt"><i style="font-size:12pt">
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style="color:rgb(33,33,33);
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del Area de Investigación de la SAC</b></font></i></b></font></i></div>
</i></font></div>
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<font style="font-size:12pt"><i style="font-size:12pt"><font
face="Garamond"><b>Ex Director del Consejo de
Aterosclerosis y Trombosis de la SAC</b></font></i></font></div>
<div style="color:rgb(33,33,33);
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font-size:15px">
<font style="font-size:12pt"><i style="font-size:12pt"><font
face="Garamond"><b>Miembro Asesor <i
style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; font-weight:400;
background-color:rgb(255,255,255)"><font
face="Garamond"><b>del Consejo de Aterosclerosis
y Trombosis de la SAC</b></font></i></b></font></i></font></div>
<div style="color:rgb(33,33,33);
font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:15px">
<i style="font-size:12pt"><font face="Garamond"><b><i
style="font-family:Calibri,Arial,Helvetica,sans-serif,"Apple
Color Emoji","Segoe UI
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Symbol","Android Emoji",EmojiSymbols;
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style="font-size:12pt"><font face="Garamond"><b><i
style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<div style="display:inline!important"><i
style="font-size:12pt"><font
face="Garamond"><b>Ex Director del
Consejo de Epidemiología y
Prevención Cardiovascular de la
SAC</b></font></i></div>
</i></b></font></i></div>
</i></b></font></i><br>
</div>
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background-color:rgb(255,255,255);
font-size:12pt"><font face="Garamond"><b><i
style="font-family:Calibri,Arial,Helvetica,sans-serif,"Apple Color
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display:inline!important"><i><font
face="Garamond"><b><i
style="font-family:Calibri,Arial,Helvetica,sans-serif">
<div style="margin:0px;
display:inline!important"><i><font face="Garamond"><b>Miembro Asesor del
Consejo de
Epidemiología y
Prevención
Cardiovascular
de la SAC</b></font></i></div>
<span> </span></i></b></font></i></div>
</i></b></font></i><br>
</i></b></font></i></div>
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<font style="font-size:12pt"><i style="font-size:12pt">
<div style="display:inline!important"><i
style="font-size:12pt"><font face="Garamond"><b>Instructor
de ACLS de la American Heart Association</b></font></i></div>
</i></font></div>
<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
face="Calibri, sans-serif" color="#000000"><b>De:</b>
Gerta Ruecker <a class="moz-txt-link-rfc2396E" href="mailto:ruecker@imbi.uni-freiburg.de"><ruecker@imbi.uni-freiburg.de></a><br>
<b>Enviado:</b> jueves, 7 de noviembre de 2019 11:41<br>
<b>Para:</b> Martin Lobo <a class="moz-txt-link-rfc2396E" href="mailto:mlobo4370@hotmail.com"><mlobo4370@hotmail.com></a>;
Viechtbauer, Wolfgang (SP)
<a class="moz-txt-link-rfc2396E" href="mailto:wolfgang.viechtbauer@maastrichtuniversity.nl"><wolfgang.viechtbauer@maastrichtuniversity.nl></a>;
<a class="moz-txt-link-abbreviated" href="mailto:r-sig-meta-analysis@r-project.org">r-sig-meta-analysis@r-project.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:r-sig-meta-analysis@r-project.org"><r-sig-meta-analysis@r-project.org></a><br>
<b>Asunto:</b> Re: [R-meta] measurement conversion is
possible ?</font>
<div> </div>
</div>
<div style="background-color:#FFFFFF">
<p>Dear Martin,</p>
<p>There is some literature on this problem, see for example
<a class="x_moz-txt-link-freetext"
href="https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbmcmedresmethodol.biomedcentral.com%2Farticles%2F10.1186%2F1471-2288-14-135&data=02%7C01%7C%7C3f71f639d9a54095704708d763908f85%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637087344854151219&sdata=nq0ylLfIqgDMCsXohvQw%2BqT2EARBTYUnUI%2F2%2FUUz7A4%3D&reserved=0"
originalsrc="https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-135"
shash="ibMcUL7wNVcgWO2l98pyri33OVUsvQ8aATNKRdPAEN5tLdj+f9KLal3KLwHZfHZPN4qISw3pyYNmVbm9RcS++PQ+ShLodwt+r7eTDFrL5/4l9aZQ6TZpqffWLMl94XoOrx5eZboam8KSaJ3bfXjBOVgxhaiaNn8c2mOFCY3cFRc="
moz-do-not-send="true">
https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-135</a></p>
<p>Best,</p>
<p>Gerta<br>
</p>
<div class="x_moz-cite-prefix">Am 07.11.2019 um 15:27
schrieb Martin Lobo:<br>
</div>
<blockquote type="cite">
<pre class="x_moz-quote-pre">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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<pre class="x_moz-quote-pre">_______________________________________________
R-sig-meta-analysis mailing list
<a class="x_moz-txt-link-abbreviated" href="mailto:R-sig-meta-analysis@r-project.org" moz-do-not-send="true">R-sig-meta-analysis@r-project.org</a>
<a class="x_moz-txt-link-freetext" href="https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstat.ethz.ch%2Fmailman%2Flistinfo%2Fr-sig-meta-analysis&data=02%7C01%7C%7C3f71f639d9a54095704708d763908f85%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637087344854161231&sdata=5r45A2KlCbnVH5Y2yV1L1ZsUFktvhpGTQb%2FsRahImHI%3D&reserved=0" originalsrc="https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis" shash="VdqbxCojwr4vfEKyxorp3U1b0uJES06H1yxUMf5RD+W7JeVR+gx7+sT6j8Gh7jeYEob6sJyrD2fXqMZNKTnDGxw00WtePIrfT0S4M/vo/Lfgv3tnMf1GCeLsHCQDC/vIIc0GwnaR72KUm8trXIKgjuKpDHBJQ8R6qUW0SwVVvbQ=" moz-do-not-send="true">https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis</a>
</pre>
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<pre class="x_moz-signature" cols="72">--
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: <a class="x_moz-txt-link-abbreviated" href="mailto:ruecker@imbi.uni-freiburg.de" moz-do-not-send="true">ruecker@imbi.uni-freiburg.de</a>
Homepage: <a class="x_moz-txt-link-freetext" href="https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.imbi.uni-freiburg.de%2Fpersons%2Fruecker%2Fperson_view&data=02%7C01%7C%7C3f71f639d9a54095704708d763908f85%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637087344854161231&sdata=dlwnYlxWB5q8qdYhfYv7keo4kNFHWXUz26jlcejUlhk%3D&reserved=0" originalsrc="https://www.imbi.uni-freiburg.de/persons/ruecker/person_view" shash="SYFd+v8p7Hvhjx2M3nbIbzk+ybS7r/xtr04ljLtkeGftz2ac0THPnK0vK18NqZ1/S2sQFyZjxV0tw5YtycgxL0FIelJFQM6blgTYuS2Twr3WAVLwvMCNjwQIakQL5GVrRvfTJ67u93tZvPuKNYcFB0ykEhZ3PwoCJWyCyZyMqyQ=" moz-do-not-send="true">https://www.imbi.uni-freiburg.de/persons/ruecker/person_view</a>
</pre>
</div>
</div>
</div>
</blockquote>
<pre class="moz-signature" cols="72">--
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: <a class="moz-txt-link-abbreviated" href="mailto:ruecker@imbi.uni-freiburg.de">ruecker@imbi.uni-freiburg.de</a>
Homepage: <a class="moz-txt-link-freetext" href="https://www.imbi.uni-freiburg.de/persons/ruecker/person_view">https://www.imbi.uni-freiburg.de/persons/ruecker/person_view</a>
</pre>
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