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Re: Something borrowed...something FAST! [RChung] [ In reply to ]
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The rule of thumb that "a delta CdA of X yield a time savings of Ys/km" does not rely on the source(s) of the difference in CdA.

The rule of thumb that "a P3C frame is 2s/km faster than a P2K frame" clearly implies that the frame is the source of the difference in CdA.

I am referring to the latter rule of thumb when I use the term "rule of thumb".

Are we clear?

Perhaps English is not your native tongue, or perhaps you are unfamiliar with the term "rule of thumb." What you're calling a rule of thumb? I don't think it means what you think it means.
I'll leave it to those reading this thread to determine which one of us is the more likely to be a non-native English speaker, Dr Chung. Maybe they'll find it ironic that you botched the sentence after the one where you imply that English isn't my native tongue.

By the way, "rule of thumb" is a rough-and-ready rule that can be applied to a variety of circumstances. Both of the rules of thumb I wrote above fit that description. The latter can apply to the P3C and P2K on a variety of courses and conditions.

It's a shame that you've chosen to hide behind deliberate obtuseness and semantic arguments. I guess if you can't debate the substance of the arguments, these are the means to which you resort.

No class.

Uh-oh. You know up above where you said you were glad to aggravate Andy and me? You sure your skin is thick enough for this? 'Cuz it appears to be time to call the waaaaaaahhmbulance.
Pathetic.
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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Pathetic.[/quote] made me laugh...
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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The issue isn't whether I doubt that there is a difference between the frames; I acknowledged that the P3C is likely to be faster than the P3C quite a few pages ago. I just don't think that the method Tom used to produce his results stands much scrutiny.
So you're willing to call someone out for botching a sentence then try to convince us the "P3C is likely to be faster than the P3C"? ;-)

--------------------------------------------------------------------
"Lemond is cycling's version of Rev Jessie Jackson." -johnnyperu 5/18/07
"Just because I suck doesn't mean my bike has to" -rickn 9/2/08
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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"It's a shame that you've chosen to hide behind deliberate obtuseness and semantic arguments. I guess if you can't debate the substance of the arguments, these are the means to which you resort."

On the one hand we have those proposing a testing methodology supported with data purporting one position, on the other hand we have another who disagrees with that position supporting his disagreement with?

How was it that you decided the p3c was faster than the alternative frame?



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Re: Something borrowed...something FAST! [brandonecpt] [ In reply to ]
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The issue isn't whether I doubt that there is a difference between the frames; I acknowledged that the P3C is likely to be faster than the P3C quite a few pages ago. I just don't think that the method Tom used to produce his results stands much scrutiny.
So you're willing to call someone out for botching a sentence then try to convince us the "P3C is likely to be faster than the P3C"? ;-)
Hey, I don't claim to be perfect. Dr Chung decided to suggest I was a non-native English speaker, so it seemed relevant to point out that he botched his next sentence (along with many others in this thread that I omitted to mention).
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Re: Something borrowed...something FAST! [Manko] [ In reply to ]
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"It's a shame that you've chosen to hide behind deliberate obtuseness and semantic arguments. I guess if you can't debate the substance of the arguments, these are the means to which you resort."

On the one hand we have those proposing a testing methodology supported with data purporting one position, on the other hand we have another who disagrees with that position supporting his disagreement with?

How was it that you decided the p3c was faster than the alternative frame?


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...on the other hand we have another who disagrees with that position supporting his disagreement with?
A well-established body of knowledge on cognitive biases? I'm pointing out weak study design. Critical appraisal doesn't necessarily involve providing alternative data or hypotheses; pointing out weaknesses in study design and potential threats to validity is part of the process of determining how strong we should consider the evidence presented in the study to be.

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How was it that you decided the p3c was faster than the alternative frame?

Well, I've acknowledged that it's unlikely, though not impossible, that the magnitude of the delta CdA attributable to positional differences and/or power meter differences is large enough to obliterate the entire observed CdA. The logical conclusion then is that the P3C is probably a faster frame.

I have a problem with adopting a "P3C is 2s/km faster than the P2K" rule of thumb based on this study, because if position changes/power meter differences account for a significant portion of the delta CdA, and based on my understanding of cognitive biases they may, then this sort of rule doesn't hold any water.

It's a shame that Drs Coggan and Chung are so willing to point out the problems in the research of others, while at the same time unwilling to acknowledge those inherent in research consistent with their methods. There is no perfect study design, and failing to acknowledge the weaknesses of a study you've designed just weakens your position. Resorting to personal insults doesn't help either.


Last edited by: donm: May 30, 08 3:15
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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It's obvious we're not getting anywhere here. Nothing substantial has been added to the debate for some time, and our positions are pretty entrenched. All we're doing now is going round in circles clarifying our positions and it's starting to get a bit personal. I'm going to leave it there.
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Re: Something borrowed...something FAST! [Andrew Coggan] [ In reply to ]
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this looks like a frigging boring thread.
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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Hey, I don't claim to be perfect. Dr Chung decided to suggest I was a non-native English speaker, so it seemed relevant to point out that he botched his next sentence (along with many others in this thread that I omitted to mention).

I guess you didn't realize that his suggesting you were a non-native speaker was a joke...which you're right, was made all the more funny by his "botching" (Hmmm...intentional or not? I guess we'll never know...) of the very next sentence :-)

From what I understand, the same comment was made to Robert not too long ago and he thought it was funny since he IS a "native English speaker". I've seen him use it a couple of times already...I guess it's part of his "shtick" now ;-)

You're taking it all too seriously. I never presented my test as a definitive study of the differences between a P2K and a P3C. The data "is what it is"...basically a simple test I did because I had the opportunity to do so, with as much as the variables as controlled as I possibly could.

To be honest though, despite the validity of your concerns about observational bias, I think you may be drastically overstating the possible effects in this case for a couple of reasons, most of which have been stated before:
  1. It's not as if I wasn't aware of the possibilities. In other words, I took great care to make sure I held the same position on each run. I've had success in the past at being able to do so, as evidenced by repeatability measurements I've been able to achieve. I'm confident I did so here as well.
  2. While doing the runs, I have absolutely ZERO feedback over what the effects of any changes I'm testing are. In fact, since I don't have a laptop I can take to the testing site, I have no idea what the results are until after arriving home and downloading the data from the head. Consciously or sub-consciously, there's no "feedback" that's available to be "acted upon" while the test is progressing.
  3. The power meter doesn't "care" which setup I may think could be faster. It's an impartial "black box". In other words, I'm not the observer, the power meter is. What sort of "observational bias" is possible with that, especially since I used the same PM for both runs and zeroed it in between?
  4. I'm a self-professed "cheapa$$". If the difference between my P2K and the P3C was small enough that I thought I could lessen or eliminate the gap by employing other "aero tricks", I would have LOVED it. There's nothing I like better than to go faster on a "garage aero special" rig than people putting out more power on the latest blinged-out setups. Now...I gotta figure out how I can get myself a better TT frame....damn. So, where's my incentive to show that the P3C is faster? It's not like I've already bought one and would suffer some serious "cognitive dissonance" if my testing showed that I'd basically wasted my money, right?


http://bikeblather.blogspot.com/
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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The issue isn't whether I doubt that there is a difference between the frames; I acknowledged that the P3C is likely to be faster than the P3C quite a few pages ago. I just don't think that the method Tom used to produce his results stands much scrutiny.
So you're willing to call someone out for botching a sentence then try to convince us the "P3C is likely to be faster than the P3C"? ;-)
Hey, I don't claim to be perfect. Dr Chung decided to suggest I was a non-native English speaker, so it seemed relevant to point out that he botched his next sentence (along with many others in this thread that I omitted to mention).

Ah. So what you're saying is, you are a native English speaker -- you're just bad at it. OK, I can live with that.
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Re: Something borrowed...something FAST! [Frank Day] [ In reply to ]
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Just to clarify, you think that observer expectancy and subject expectancy effects are far-fetched? They do sound far-fetched until you realise how powerful and well-supported by a massive body of literature they are. As both subject and observer in his study, the potential for Tom's expectancy to bias the results is enormous. If you design a study like this, you may find what you expect to find, but it doesn't make it true.

When your kid's forehead feels hot, do you hand the thermometer to 8 different people to take her temperature? If not, how do you know that your observer expectancy hasn't rendered any rule of thumb that says, "my kid's temperature is 40C and needs to be reduced" invalid?
While this seems like a straight forward example, taking a temperature, while seeming simple, is filled with potential error. Most of the errors would lead to a "too low" reading but some can result in "too high". Was the thermometer shook down properly after the last temp for instance. Or, did mom just give the kid some hot soup or tea and you come in to take the temperature. The kid may try to manipulate the temperature if he knows the right number will keep him out of school or keep him out of the ice bath.

It is unlikely that observer bias would play a role in taking a temperature, but it certainly does in taking a simple measurement like blood pressure. People keep taking it until they get the number they want, then take that one.

All measurements are prone to error and due care must be used in both obtaining the measurement and in interpreting it (if the kids temp is measured as 40C but he is happily playing video games, does one necessarily believe it?).

I think the thermometer example is a good one. We're not too concerned whether the true temperature is 39.9 or 40.1; what we're typically interested in is whether the measured temperature is greater than or less than the rule of thumb threshold for a fever. We don't give that thermometer to 8 other people and ask them to repeat the reading because we already have an idea of what the precision is for this device, and how to relate the measurement to other observations about the patient's condition. We know those things because we've used thermometers many, many times in the past and have learned how to use it, to interpret it, and how to recognize that a reading of 30C or 50C is way outside the usual precision. Not knowing whether the true temperature is 39.9 or 40.1 does not invalidate the rule of thumb "higher than 38 means a fever." It's a rule of thumb.

In this case, Tom has used this method many, many times in the past and has learned how to do it, to interpret the results, and to recognize when the results are spoiled (as he did for the final run). The measured difference in CdA is an order of magnitude greater than his usual precision.
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Re: Something borrowed...something FAST! [RChung] [ In reply to ]
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Just to clarify, you think that observer expectancy and subject expectancy effects are far-fetched? They do sound far-fetched until you realise how powerful and well-supported by a massive body of literature they are. As both subject and observer in his study, the potential for Tom's expectancy to bias the results is enormous. If you design a study like this, you may find what you expect to find, but it doesn't make it true.

When your kid's forehead feels hot, do you hand the thermometer to 8 different people to take her temperature? If not, how do you know that your observer expectancy hasn't rendered any rule of thumb that says, "my kid's temperature is 40C and needs to be reduced" invalid?
While this seems like a straight forward example, taking a temperature, while seeming simple, is filled with potential error. Most of the errors would lead to a "too low" reading but some can result in "too high". Was the thermometer shook down properly after the last temp for instance. Or, did mom just give the kid some hot soup or tea and you come in to take the temperature. The kid may try to manipulate the temperature if he knows the right number will keep him out of school or keep him out of the ice bath.

It is unlikely that observer bias would play a role in taking a temperature, but it certainly does in taking a simple measurement like blood pressure. People keep taking it until they get the number they want, then take that one.

All measurements are prone to error and due care must be used in both obtaining the measurement and in interpreting it (if the kids temp is measured as 40C but he is happily playing video games, does one necessarily believe it?).

I think the thermometer example is a good one. We're not too concerned whether the true temperature is 39.9 or 40.1; what we're typically interested in is whether the measured temperature is greater than or less than the rule of thumb threshold for a fever. We don't give that thermometer to 8 other people and ask them to repeat the reading because we already have an idea of what the precision is for this device, and how to relate the measurement to other observations about the patient's condition. We know those things because we've used thermometers many, many times in the past and have learned how to use it, to interpret it, and how to recognize that a reading of 30C or 50C is way outside the usual precision. Not knowing whether the true temperature is 39.9 or 40.1 does not invalidate the rule of thumb "higher than 38 means a fever." It's a rule of thumb.

In this case, Tom has used this method many, many times in the past and has learned how to do it, to interpret the results, and to recognize when the results are spoiled (as he did for the final run). The measured difference in CdA is an order of magnitude greater than his usual precision.
Look, you are justifying your acceptance of this result because you have learned to trust Tom. Your trust does not make for a strong "study". submit this study to a publication and tell them it should be published because you have come to trust this guy and I suspect the laughter would be heard a long ways away. It might be true but there are lots of perfectly valid reasons others might question the result, especially when the entirety of the measured change is attributed to the frame. It is simply mind boggling to me that those of you who are so critical of the attempts of others to quantify changes are so accepting of this result and critical of others who are simply presenting reasons why the result should be questioned.

Oh, and the rule of thumb for "fever" isn't particularly good one. For instance, my normal is about 36. When I have a temperature of 37, I am usually pretty sick. What is normal for others is a "fever" for me.

--------------
Frank,
An original Ironman and the Inventor of PowerCranks
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Re: Something borrowed...something FAST! [Frank Day] [ In reply to ]
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Look, you are justifying your acceptance of this result because you have learned to trust Tom. Your trust does not make for a strong "study". submit this study to a publication and tell them it should be published because you have come to trust this guy and I suspect the laughter would be heard a long ways away. It might be true but there are lots of perfectly valid reasons others might question the result, especially when the entirety of the measured change is attributed to the frame. It is simply mind boggling to me that those of you who are so critical of the attempts of others to quantify changes are so accepting of this result and critical of others who are simply presenting reasons why the result should be questioned.

Oh, and the rule of thumb for "fever" isn't particularly good one. For instance, my normal is about 36. When I have a temperature of 37, I am usually pretty sick. What is normal for others is a "fever" for me.

Your argument was that n=1 and the experiment wasn't blinded. When you take your temperature, do you blindfold yourself and have eight others check every reading?
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Re: Something borrowed...something FAST! [Tom A.] [ In reply to ]
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Thanks for the well-reasoned response, Tom. I appreciate you taking the time. It also looks like you've kept your results in the proper perspective and are willing to at least acknowledge and address concerns over subject/observer bias.
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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Thanks for the well-reasoned response, Tom. I appreciate you taking the time. It also looks like you've kept your results in the proper perspective and are willing to at least acknowledge and address concerns over subject/observer bias.
iow nothing has changed from his initial post. You are just finally understanding it.
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Re: Something borrowed...something FAST! [OT in CA] [ In reply to ]
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Thanks for the well-reasoned response, Tom. I appreciate you taking the time. It also looks like you've kept your results in the proper perspective and are willing to at least acknowledge and address concerns over subject/observer bias.
iow nothing has changed from his initial post. You are just finally understanding it.
I don't agree with all of what he's written but, as I said above, we're going round in circles re-stating and clarifying our positions, so I chose not to continue the debate. I do appreciate his taking the time to respond in a reasonable way.
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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Maybe they'll find it ironic that you botched the sentence after the one where you imply that English isn't my native tongue.

How so? Sentence fragments are quite common in normal speech, and even in informal/conversational/literary writing.
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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As someone who has done a lot of field testing, I think you may be ascribing a cognitive bias to a physical endeavor that under most situations doesn't apply--or in this instance, applies evenly.

For instance, I don't doubt that Tom's CxA could actually be higher than reported. What I doubt, though is that the test results would be different for the P2K tests, simply because the 'optimization tweaks' that you're suspecting occurred with the P3C happened with his many tests on the P2K. If he had never tested his position on the P2K prior to this test, I think this line of argument would hold a little more water.

Here would be one suggestion for minimizing any conscious or subconscious position tweaks: do the field test runs at a more realist power output. I don't know anything about Tom's venue, so this may not be possible. If it is, though, it practically eliminates the 'sandbagging' aspect of testing the position; i.e. at race power (or above), you're going to end up gravitating to the position in which you actually ride.
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Re: Something borrowed...something FAST! [Andrew Coggan] [ In reply to ]
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How so?

Hey, is English your native tongue? 'Cuz a sentence that ain't.
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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That's good, just fall back on the "trust me, I'm an authority on these matters" argument.

I was merely making clear the basis for my opinion. What I'd like to know is, what is the basis for yours? Oh, right: a vaguely-described "...background in psychology and medicine..." and an admitted lack of any practical experience whatsoever in this area. Do you think that would qualify you as an expert reviewer for, say, a scientific journal?
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Re: Something borrowed...something FAST! [donm] [ In reply to ]
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Critical appraisal doesn't necessarily involve providing alternative data or hypotheses; pointing out weaknesses in study design and potential threats to validity is part of the process of determining how strong we should consider the evidence presented in the study to be.

Given your lack of experience in this area, do you believe that you qualifed to judge what is or isn't an important weakness?

To put it another way: do you think that the NIH should ask you to review grant applications regarding cognitive bias? If so, why, and if not, why not?
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Re: Something borrowed...something FAST! [RChung] [ In reply to ]
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How so?

Hey, is English your native tongue? 'Cuz a sentence that ain't.
Say what? ;-)
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Re: Something borrowed...something FAST! [RChung] [ In reply to ]
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How so?

Hey, is English your native tongue? 'Cuz a sentence that ain't.

Fetchez la vache !
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Re: Something borrowed...something FAST! [eb] [ In reply to ]
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How so?

Hey, is English your native tongue? 'Cuz a sentence that ain't.

Fetchez la vache !

Fuckez le dog!

I thought it was kinda amusing that donm started talking smack then whined after he showed up for a knife fight carryin' a spoon.
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Re: Something borrowed...something FAST! [OT in CA] [ In reply to ]
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Thanks for the well-reasoned response, Tom. I appreciate you taking the time. It also looks like you've kept your results in the proper perspective and are willing to at least acknowledge and address concerns over subject/observer bias.
iow nothing has changed from his initial post. You are just finally understanding it.
Bingo!!!!

Rik
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