Catherine DeSoto and Robert Hitlan have published an FAQ site Frequently Asked Questions about DeSoto and Hitlan (2007) to answer questions and refute some inaccurate, misleading and even erroneous critiques of their important article published in the November 2007 article of the Journal of Child Neurology Blood levels of mercury are related to diagnosis of autism: A reanalysis of an important data set. Most of the FAQ deals with questions raised on Autism Street in A Tale of Two Tails by bloggers Interverbal and Do'C. The two bloggers published a critical review of he DeSoto and Hitlan paper on Autism Street. The Desoto-Hitlan FAQ site exposes many information gaps in the Interval-Do'C critique.
DeSoto and Hitlan responded very politely to the critique and the FAQ site is important reading for anyone with a serious interest in autism, although it will undoubtedly be difficult for many of the 87 Autism Street cheerleaders who published their gloating sarcastic commentaries to read with an open mind. Interverbal posted an interesting comment:
Comment by Interverbal — 18 November, 2007 @ 4:06 pm At this time I don’t think we have any plans to write a letter to the editor. Speaking only for myself, I am anxious to see how Ip et al respond to DeSoto & Hitlan.
As one who does not share Interval's and Do'C's knowledge of statistical methodologies I might have been confused in saying that I too look forward to any reply by Ip et al. As I read DeSoto and Hitlan's FAQ it appears to me that they are saying that Ip et al already acknowledged their errors by the time the DeSoto article was published in November:
Q. Why did you take the time to write about a mistake that had already been corrected by the authors?
A. We didn’t. The mistake had not been found until we found it. We are the correctors. Again, some blog sites have unfortunately served to confuse this issue.
Q. What was really so wrong with the Ip 2004 article?
A. Based on their retraction which appeared in the same issue issue as our article, the mean for the autistic group was wrong, the standard deviations were wrong for both groups, the stated statistical significance in 2004 was way off. The means as they reported them in 2004 result in a significant t test by any standard…meaning that the autistic group had significantly more mercury in their blood than the control group. This is indisputable (or should be). It would not matter if a one tailed or a two tailed test was used. All interested parties should use their original data from the 2004 article and calculate the t value and p value (or put the numbers into an online t test calculator-- see "how can I check the original numbers myself?"). Their original stated level of statistical probability was off by almost 10 fold.
The data set they provided in 2007 misses conventional significance by a hair using their original statistical technique. Some blog sites such as Age of Autism have also pointed out that Ip et al overstated their findings in 2004. This means that the conclusions they made reached way beyond their findings. This is less serious compared to flubbing your stats, but I will note it for completeness.
If I am right in my reading of the DeSoto and Hitlan FAQ site commentary then I assume that Interval and Do'C will publish a retraction of their analysis on Autism Street. I will hold my breath until then. No, no ... on second thought ... I better not. I don't know if Interval and Do'C have the integrity to admit error. My lungs could explode, or I could implode, waiting for the retraction.
Too bad Interval didn't write that letter to the editor.