Sunday, January 08, 2006

Tom vs RCT: 2nd round.

Some time ago, I discussed the Lidcombe random control trial (RCT) and why I believe they need to revise their statistical measures: see here, and here.

Mark Jones et al. have responded to the rapid responses, but they have not directly responded to the arguments put forward in my rapid response. For example, they say that
"... spontaneous recovery has been a recurring theme in the rapid responses to our article... The rate of natural recovery from stuttering in young children in the general population has been estimated at 74%(1), but in clinical populations with this condition this estimate is expected to be much lower...Evidence from a previous study(2) suggests that approximately 40% of children identified as stuttering had the condition for less than 6 months."
However, they do not directly relate this or other statements to my arguments to disprove my case, so it is difficult for me to respond in a constructive way. My guess is that they imply that any effect due to the spontaneous recovery rate on the statistics is very small because the rate in the clinical setting is only about 40% and not about 75%. But this argument is not correct. The great irony is that the closer the recovery rate is to 50%, the greater the impact on the statistics!! :-) So by claiming a 40% rate instead of a 74%, they have actually strengthened my argument that they need to revise the statistical significance and effect size of their study to take into account the natural recovery rate!

I have sent a response, where I explain in more details. The response should be on-line in one or two days. Check here.

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