Firewall Wizards mailing list archives
Re: Flawed Surveys [was: VPN endpoints]
From: "Marcus J. Ranum" <mjr () ranum com>
Date: Wed, 01 Sep 2004 12:52:44 -0400
Paul D. Robertson wrote:
or the CIO magazine survey on security) - a lot of these surveys are fundamentally flawed. They yield results but it's hard to say what the results actually _measured_.So long as they're flawed approximately the same way from survey to survey, they're often both "better than nothing[1]" and a good relative metric.
Sorry, but you're completely wrong about that. The reason is because if you have a survey of unknown bias, you can't assume that the bias does not change because of other factors, because the bias is unknown. In other words, unless you know how wrong it is and why, you can't be sure it's wrong the same way twice.
We often don't need absolute metrics, relative metrics will do just fine.
Be careful; polls are opinion measures, not metrics. Metrics would be if you were (for example) pulling actual data from corporate financials regarding security expenditures. Measuring someone who claims to be CIO's opinion about what their expenditures either {are|should be} is not even good enough to give a relative metric. What I think you're saying, unfortunately, is "having some 'gee wow' numbers is good enough to blow some basic FUD and we need basic FUD so it's OK."
I know what my $foo risk was last year, and I know what it was the year before, and I can compare to the survey and see the relative differences and the relative change- therefore, I can figure out my approximate relative change for this year.
But that's the problem. You don't actually "know" anything. You have some information that is based on a self-selected sample which I guarantee you will change next year. Different people will be bored enough to answer the survey, and the answers they give will be either more or less misinformed than they were last year. There are no constants *whatsoever* in these surveys. Now, if you said you were going to take the same self-selected sample and poll those same people next year, you're starting to apply some controls to your survey, but they're still not going to be good enough to give you a result worth having.
- How much the person cared about the topic (motive to respond) - How honest the respondent is (hard to verify) - Other factors (hard to predict)You can also (a) drop outliers
You can't drop outliers because, since you actually know nothing about your data's provenance, you don't know what an "outlier" is when you're dealing with a self-selected sample. You might, for example, discard the survey response from the one *REAL* CIO who answers the survey! You simply do not know. What you're trying to do is apply science to pseudoscience. The result is comparable to polishing a turd: if you work at it hard enough, it still won't get shiny.
, (b) have cross-conflicting questions
That simply measures consistency in response; not whether it is truthful or whether your sample is biassed.
(c) answer the questions on behalf of a known quantity and still be able to validate polls pretty well. You obviously don't get people who don't care to respond, but if the number of people who do respond is significant, that's ok.
NO IT IS NOT OK! ________________ I am sorry, Paul - if you believe the statement you made above, you really really really need to read a few introductory texts on statistics, the scientific method, and research methods. Your statements above amount, to a trained statistician, as comparable to a declaration that not only is the earth flat, but it rests on the back of a turtle. I wasn't originally aiming my rant at Paul (I seem to be ranting at my buddies a lot these days...) but it is exactly the kind of tolerance of pseudo-science that Paul is advocating above that keeps security a "social science" rather than something measurable or quantifiable. Security practitioners are on the verge of understanding that we need to sell security in terms of ROI and risk, and it's just BEGINNING to sink in that risk requires real metrics and statistics. But we're still stuck with a lot of pseudo-science.
I'm sure nobody on this list has ever filled out one of those surveys from a magazine in which they asked you your job position, whether you were a decision-maker, company size, etc... And I'm sure you all fill them out EXACTLY right. I used to enjoy periodically asserting that I was the CEO of a 1 person company with a $4,000,000 IT budget (well, a guy can dream, huh?) Unfortunately, sometimesYou're out of the range of the mean by orders of magnitude, anyone doing it even half-way should be throwing that response away (assuming they *want* correct data,)
ARRGH!! NO! NO MORE PSEUDO-SCIENCE! YOU ARE HURTING MY BRAIN!!!!!! MY HEAD IS GOING TO EXPLODE!!! Paul, if you are a scientist and you measure data, and then decide to throw away values that don't match your expectations, that's called "experimental fraud"!! That's um, bad! See, the problem is that you can't a priori decide you know what your mean _is_ until you know what your data is. So what if 50% of your self-selected sample all were feeling frisky that day and entered bogus figures? How _many_ values around the mean will you throw away until you get a number that "feels right"??? That's how psychic researchers get their results: they know what they want to find and throw away data until it "feels right"??? There is no amount of compensating controls you can use to polish a turd into a useful result. And, more importantly, at a certain point, the cost of polish exceeds the cost of doing it right in the first place!! Reading list: - "How to Lie with Statistics" - Darrell Huff ISBN: 0393310728 - "Research Design and Methods" (4th ed) Bordens and Abbott ISBN: 0767421523 - Richard Feynman's article on experimental controls and their mis-application in social "sciences" from "the pleasure of finding things out" (I think it's that book..) mjr. _______________________________________________ firewall-wizards mailing list firewall-wizards () honor icsalabs com http://honor.icsalabs.com/mailman/listinfo/firewall-wizards
Current thread:
- Re: VPN endpoints Kevin Sheldrake (Sep 01)
- <Possible follow-ups>
- Re: VPN endpoints Paul D. Robertson (Sep 01)
- Re: Flawed Surveys [was: VPN endpoints] Marcus J. Ranum (Sep 01)
- Re: Flawed Surveys [was: VPN endpoints] Paul D. Robertson (Sep 01)
- Re: Flawed Surveys [was: VPN endpoints] Marcus J. Ranum (Sep 01)
- Re: Flawed Surveys [was: VPN endpoints] Paul D. Robertson (Sep 01)
- Re: Re: Flawed Surveys [was: VPN endpoints] Christopher Hicks (Sep 01)
- Re: Flawed Surveys [was: VPN endpoints] Marcus J. Ranum (Sep 01)
- Re: Re: Flawed Surveys [was: VPN endpoints] Bruce B. Platt (Sep 01)
- RE: Re: Flawed Surveys [was: VPN endpoints] Tina Bird (Sep 01)
- Re: Re: Flawed Surveys [was: VPN endpoints] Bruce B. Platt (Sep 01)
- RE: Re: Flawed Surveys [was: VPN endpoints] Tina Bird (Sep 01)
- Re: Re: Flawed Surveys [was: VPN endpoints] Bruce B. Platt (Sep 01)
- Wired article on the scientific method Tina Bird (Sep 01)