PPRuNe Forums CEP assessment
 User Name Remember Me? Password Forgotten your Username/Password?
 Register Forms FAQ Calendar Advertise Mark Forums Read

 Flight Testing A forum for test pilots, flight test engineers, observers, telemetry and instrumentation engineers and anybody else involved in the demanding and complex business of testing aeroplanes, helicopters and equipment.

 14th Apr 2011, 08:10 #1 (permalink) Join Date: Oct 2010 Location: India Age: 37 Posts: 42 CEP assessment This is the CEP related doubt that I have. Going by the definition of CEP i.e. if CEP is n meters, 50% of rounds land within n meters of the target, 43% between n and 2n, and 7 % between 2n and 3n meters, and the proportion of rounds that land farther than three times the CEP from the target is less than 0.2%. Now to say for example, if the min and max error in a measurement is 0% and 2% respectively, then value of 3n=2% (ignoring the area for 0.2% of the rounds discussed above). If that be so then n=0.67%, and hence it may be correct to say that in 50% of the measurements made there is a likelihood of 0.67% error, for 93% of the measurements made (within '2n' metres: i.e. including the n and the 2n areas ;50%+43%) there is a likelihood of 1.34% error (2n value) and for 100% of the measurements a probability of 2% error (within 3n area) exists. Well this is where I could reach given my very basic understanding in mathematics. Would request the august audience to guide me for corrections. Thanks
 15th Apr 2011, 16:43 #2 (permalink) Join Date: Feb 2005 Location: KPHL Posts: 341 peeush, I don't see the flight test relevance to your question. It seems like you're trying to use a normal distribution on measurement errors, by assuming that the maximum range of measurement errors is equivalent to three standard deviations, and from there deducing that half of your measurements have a measurement error of one third of the maximum. For that to work you need to identify all sources of measurement error and confirm that each is error is idendependant of all others. Once you've done that, you can claim a probability that 50% of the measurements are within n/3, but you cannot state that it is so. On average 50% of coin flips will turn up heads, that doesn't mean you won't ever see 10 heads in 10 flips. Matthew.
 16th Apr 2011, 04:23 #3 (permalink) Join Date: Oct 2010 Location: India Age: 37 Posts: 42 Matthew, Thanks for the comments, I would like to confirm the following:- 1. The errors taken into calculations are independent of each other. 2. It is understood that there would only be a probability of n/3 errors occuring in 50% of the cases and 2n/3 in 93% of the cases. Given the above statements, it would imply that if I have a max error of 2% in system, for 50% of the cases I may expect a probability of 0.67% error, for 93% of the cases 1.34% error and so on (in accordance with the CEP definition stated in the original post) Thats what I finally intended to confirm. Thanks
 This ad will disappear if you login

 Thread Tools

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

All times are GMT. The time now is 18:59.

 Privacy Policy - Terms and Conditions - Contact Us - PPRuNe Home - Archive - Top

vBulletin® v3.8.7, Copyright ©2000-2013, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
© 1996-2012 The Professional Pilots Rumour Network

 As these are anonymous forums the origins of the contributions may be opposite to what may be apparent. In fact the press may use it, or the unscrupulous, or sciolists*, to elicit certain reactions. *"sciolist"... Noun, archaic. "a person who pretends to be knowledgeable and well informed".