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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Original Message
Apparently, I'm just not getting through
Posted by E-Stat on June 22, 2010 at 09:11:15:
Sadly, it in not possible to conduct a comparative test without switching between the two things under comparison.
Uh, yeah. Do we have anyone in the audience who doesn't understand this? :)
While It is possible to have a person at each end to switch the physical cables, this is not as fast and as others doing blind testing have found, the people doing the switching can intentionally or more often unintentionally affect the test consistence with what they belive.
And the assumptions keep rolling in... I've used my wife (a university pharmacy professor) to proctor changes. First of all, she doesn't even know which cable should be "better". Secondly, and more importantly, I've left the room through one door and she enters through another where there is no opportunity for visual cues. And no, she doesn't stamp her foot once with one choice and twice for another. :)
Thus, having a switch which represented a few inches of the best cable under consideration, when that cable is 10 to 30 feet long, represents an insignificant effect.
Your response is a perfect example of the pitfalls of substituting assumptions for empirical data. The obvious concern is not the effect of a "few inches" of cable. It is that the switch exhibits crosstalk such that you are not comparing A with B. You are comparing AB with AB. All that you had to do to answer my repeated questions about first establishing a control is reply "No, I did not use a control. I assume that the box exhibits perfect isolation between the cables and that it has no possible effect on the outcome.
I guess your test system is likewise an irrelevant part of the test. I'll stop here since you seem to have difficulty with simple, direct answers. Thanks anyway!
rw