Tag Archives: Statistics

This (does not equal) That

Lesson: Correlation does not imply causation

Also See: Spurious Correlations


Spurious Correlations(click image for much larger view)

What Is The Birthday Paradox?

Note from Mason I. Bilderberg

How many people must be in a group for the odds of two people in the group having the same birthday reaches a statistical likelihood better than 50%?

The number is so surprisingly few that some people attribute a birthday match in such a small group to something akin to a sign from the heavens. They ask, “What are the odds?”

But did you know, in a group of 50 people, there is a 97% statistical chance of two people having the same birthday? Psychics use these types of statistical illusions to give audiences the impression that such occurrences are “a sign from above!”

I’d love to be in a group of 50 people when it is discovered that two people have the same birthday and the psychic asks in a mysterious tone, “What ARE the odds?” . . . just so i can yell back “97% you freakin’ charlatan!”

Wikipedia explains all the math, as does the video below.

🙂


Via BrainStuff

The Seralini GMO Study – Retraction and Response to Critics

steven_novellaby via Science-Based Medicine

Elsevier has announced that they are retracting the infamous Seralini study which claimed to show that GMO corn causes cancer in laboratory rats. The retraction comes one year after the paper was published, and seems to be a response to the avalanche of criticism the study has faced. GMOs 822_300pxThis retraction is to the anti-GMO world what the retraction of the infamous Wakefield Lancet paper was to the anti-vaccine world.

The Seralini paper was published in November 2012 in Food and Chemical Toxicology. It was immediately embraced by anti-GMO activists, and continues to be often cited as evidence that GMO foods are unhealthy. It was also immediately skewered by skeptics and more objective scientists as a fatally flawed study.

The study looked at male and female rats of the Sprague-Dawley strain of rat – a strain with a known high baseline incidence of tumors. These rats were fed regular corn mixed with various percentages of GMO corn: zero (the control groups), 11, 22, and 33%. Another group was fed GMO corn plus glyphosate (Round-Up) in their water, and a third was given just glyphosate. The authors concluded:

The results of the study presented here clearly demonstrate that lower levels of complete agricultural glyphosate herbicide formulations, at concentrations well below officially set safety limits, induce severe hormone-dependent mammary, hepatic and kidney disturbances. Similarly, disruption of biosynthetic pathways that may result from overexpression of the EPSPS transgene in the GM NK603 maize can give rise to comparable pathologies that may be linked to abnormal or unbalanced phenolic acids metabolites, or related compounds. Other mutagenic and metabolic effects of the edible GMO cannot be excluded.

Sounds pretty scary. Now let’s look at the multiple criticisms:

The biggest criticism of the study is the combination of two features – the small sample size and lack of statistical analysis. The entire study is premised on comparing various dose groups with control groups that were not exposed to GMO or glyphosate. And yet, the authors provide no statistical analysis of this comparison. Given the small number of rats in each group, it is likely that this lack of statistical analysis is due to the fact that statistical significance could not be reached.

In other words – the results of the study are uninterpretable. In the retraction statement Elsevier wrote:

Ultimately, the results presented (while not incorrect) are inconclusive, and therefore do not reach the threshold of publication for Food and Chemical Toxicology.

The retraction reads like a long excuse for the editorial failure of the journal, and is disappointing. But at least they ultimately reached the correct conclusion – this paper should never have been published. It slipped through the cracks of peer review.

MORE . . .

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