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Unread 30-06-2015, 13:59
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Re: "standard error" of OPR values

Quote:
Originally Posted by Ether View Post

I think you missed my point entirely.



Yes, they can be computed, but that doesn't mean they are statistically valid. They are not, because the data does not conform to the necessary assumptions.



Yes they are, but they are also nearly all the same value... which is obviously incorrect... and a result of assumptions which the data does not meet.



Lack of independence is only one of the assumptions which the data do not meet.



They are not being ignored "because they show how poor the OPR estimators are performing"; they are not being reported because they are invalid and misleading.



There are better metrics to report to show how poorly the estimators perform.



But based on this response, the OPR estimates themselves should not be reported because they are not statistically valid either. Instead by not reporting some measure of the potential error, they give the impression of precision to the OPRs.

I just discussed this problem as a major failing for engineers in general--if they are not fully comfortable in reporting a parameter, e.g., a measure of uncertainty, they often will simply ignore the parameter entirely. (I was discussing how the value of solar PV is being estimated across a dozen studies. I've seen this tendency over and over in almost 30 years of professional work.) Instead, the appropriate method ALWAYS, ALWAYS, ALWAYS is to report the uncertain or unknown parameter with some sort of estimate and all sorts of caveats. Instead what happens is that decisionmakers and stakeholders much too often accept the values given as having much greater precision than they actually have.

While calculating the OPR really is of no true consequence, because we are working with high school students who are very likely to be engineers, it is imperative that they understand and use the correct method of presenting their results.

So, the SEs should be reported as the best available approximation of the error term around the OPR estimates. And the caveats about the properties of the distribution can be reported with a discussion about the likely biases in the parameters due to the probability distributions.
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