Learning material for Cochrane reviewers // Material didáctico para revisores de Cochrane

This is a link with leanring material for those intending to do (or already engaged in) a systematic review for the Cochrane library. You can consult it on screen or print the 196 page PDF file.

http://www.cochrane-net.org/openlearning/


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Este es un enlace con material didáctico para los interesados en realizar (o ya involucrados en) una revisión sistemática para la Cochrane. Puede consultarse en pantalla o imprimirse un documento PDF de 196 páginas.

http://www.cochrane-net.org/openlearning/

RevMan tutorial in Youtube // Tutorial RevMan en Youtube

You can see a tutorial of the RevMan (the program used to do the Cochrane reviews) in this links:

Part 1
http://www.youtube.com/watch?v=P6susM9BT0A

Part 2
http://www.youtube.com/watch?v=VqcNJ0UkGhg&feature=relmfu

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Podeis ver un tutorial sobre RevMan (el programa que se utiliza para realizar las revisiones sistemáticas de Cochrane) en estos enlaces:

Parte 1
http://www.youtube.com/watch?v=P6susM9BT0A

Parte 2
http://www.youtube.com/watch?v=VqcNJ0UkGhg&feature=relmfu

Bayesian inference // Inferencia bayesiana

Links in English:

http://www.astro.cornell.edu/staff/loredo/bayes/


Links in Spanish:

http://www.ugr.es/~mcdiaz/bayes/


http://dxsp.sergas.es/ApliEdatos/Epidat/Ayuda/9-Ayuda%20An%E1lisis%20bayesiano.pdf


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Links en inglés:

http://www.astro.cornell.edu/staff/loredo/bayes/


Enlaces en español:


http://www.ugr.es/~mcdiaz/bayes/


http://dxsp.sergas.es/ApliEdatos/Epidat/Ayuda/9-Ayuda%20An%E1lisis%20bayesiano.pdf

A billion dollars for the winner!

How big is a billion? Beware, this is a tricky question. If you come from Europe you will probably answer “one million millions” (that is 1 followed by 12 zeros, or 10 to the 12^th power), but if you are American or Canadian, you will say “one thousand millions” (1 followed by 9 zeros, or 10 to the 9^th power).

This is the definition of billion from The Oxford Dictionary available online:

“In British English, a billion used to be equivalent to a million million (i.e. 1,000,000,000,000), while in American English it has always equated to a thousand million (i.e. 1,000,000,000). British English has now adopted the American figure, though, so that a billion equals a thousand million in both varieties of English.

The same sort of change has taken place with the meaning of trillion. In British English, a trillion used to mean a million million million (i.e. 1,000,000,000,000,000,000). Nowadays, it's generally held to be equivalent to a million million (1,000,000,000,000), as it is in American English.”

http://oxforddictionaries.com/words/how-many-is-a-billion

The word billion apparently entered English from French in the 17^th century, although its first recorded uses date from the 13^th century.

In Spanish, as I mentioned before, “billón” is a million millions:

http://buscon.rae.es/draeI/SrvltConsulta?TIPO_BUS=3&LEMA=billon

The same goes for French, German, and most of the languages in mainland Europe. 

Using the billion with 12 zeros is usually referred to as the “long scale”, the billion with 9 zeros being known as the “short scale”.  A very interesting and complete article about the subject may be found here:

http://en.wikipedia.org/wiki/Long_and_short_scales#cite_note-Smith-11

PLEASE ADD YOUR COUTRY AND THE NUMBER OF ZEROS THAT A "BILLION" HAS FOR YOU
Use the "comment" tool

Like this

SPAIN......12 zeros

SAMPLE SIZE CALCULATION // Cálculo de tamaño de la muestra

If you need a tool to calculate your sample size, you may want to try these links:

http://www.pwpamplona.com/wen/calcu/calculadora1.htm
An easy to use calculator from Navarra (Spain). In Spanish.

http://www.stat.ubc.ca/~rollin/stats/ssize/
A series of Java Script tools by Rollin Brant (University of British Columbia) to calculate sample size in the most frequent situations.

http://www.epibiostat.ucsf.edu/biostat/sampsize.html
A very complete web link from UCSF

http://biostat.mc.vanderbilt.edu/wiki/Main/PowerSampleSize
A free program from Vanderbilt University, by William Dupont and Walter Plummer.

http://hedwig.mgh.harvard.edu/sample_size/size.html
By David Schoenfeld , from the Massachusetts General Hospital- Harvard University.

http://www.sealedenvelope.com/power_binary.php
They also have a tool to create a randomisation list:
https://www.sealedenvelope.com/freerandomiser/v1/lists



More links in Spanish:
http://www.fisterra.com/mbe/investiga/9muestras/9muestras2.asp

http://www.psico.uniovi.es/Dpto_Psicologia/metodos/tutor.7/p3.html

http://www.seh-lelha.org/tamuestra.htm



Thanks for reading!

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Si quieres calcular el tamaño de tu muestra, quizá te interese probar los siguientes enlaces:


http://www.pwpamplona.com/wen/calcu/calculadora1.htm
Una calculadora fácil de usar de la Universidad de Navarra (España)

http://www.stat.ubc.ca/~rollin/stats/ssize/
Una serie de herramientas Java por Rollin Brant (Universidad de British Columbia), para calcular el tamaño de la muestra en las situaciones más frecuentes

http://www.epibiostat.ucsf.edu/biostat/sampsize.html
Un enlace muy completo de la Universidad de California San Francisco

http://biostat.mc.vanderbilt.edu/wiki/Main/PowerSampleSize
Un programa gratuito de la Vanderbilt University, por William Dupont y Walter Plummer.

http://hedwig.mgh.harvard.edu/sample_size/size.html
Por David Schoenfeld , del Massachusetts General Hospital- Harvard University.

http://www.sealedenvelope.com/power_binary.php
También tienen una herramienta para aleatorización en este enlace:
https://www.sealedenvelope.com/freerandomiser/v1/lists


Más enlaces en español:
http://www.fisterra.com/mbe/investiga/9muestras/9muestras2.asp

http://www.psico.uniovi.es/Dpto_Psicologia/metodos/tutor.7/p3.html

http://www.seh-lelha.org/tamuestra.htm


Gracias por leer!

How many tails do you have, if you’ll forgive the expression?

Q: I have been told that my distribution is “single tailed”. What does it mean? Is this something I should feel guilty about?

A: Not at all. In fact it has nothing to do with your anatomy. Here is the explanation of its meaning:
Generally speaking, when you are testing a hypothesis you want to know if there is any difference between two treatments.
If there is no difference, we call it “null hypothesis”, (“nullus” meaning “not any” in Latin), and statisticians always make this a priori assumption. If, after the statistical test, they find no difference between treatments, they assume the NULL HYPOTHESIS. If, on the contrary they find a difference, they REJECT the null hypothesis, and therefore accept the ALTERNATIVE HYPOTHESIS. That is how it works. 

Now, pay attention: If you are comparing A against PLACEBO, there is only ONE possible alternative hypothesis (The null hypothesis is A is equal to placebo, i.e. there is no difference between them):
A is better than placebo
(…but you would not even consider the possibility that placebo is better than A, because that would mean that A, instead of a treatment, is a risk factor).


But if you are comparing drug A against drug B, then we have TWO possible alternative hypotheses:
A is better than B
B is better than B

In the first case (A against placebo) we call it a SINGLE-TAILED distribution. In the second (A against B) we call it DOUBLE-TAILED a distribution.

And, to answer a message from a male reader of the blog (in case some others share the same doubt): no, double tailed distributions will not enhance your sexual life. You have a terrible misconception. 

Thanks for reading

CTSPEDIA

This is a link kindly suggested by Prof. Frank Harrel (University of Vanderbilt, USA).
CTSPEDIA is a collection of tools, educational materials and others. It deals with clinical, statistical and translational knowledge, and it is a good homepage for your internet browser too (I mean it), because it has so many useful things just a click away. CTSPEDIA is funded by an award from the NIH. Hope you enjoy it.

http://www.ctspedia.org/do/view/CTSpedia