# Interpreting Q-Q Plots

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## Interpreting Q-Q Plots

 My understanding of Q-Q plots is that if the tails of the plotted points fall above or below the x=y line the distribution of observed/measured values is under or over dispersed. But, how do I interpret measured values that are in horizontal lines? The attached plot illustrates this situation. TIA, Rich______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code. chromium_norm.pdf (8K) Download Attachment
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## Re: Interpreting Q-Q Plots

 Tena koe Rich Probably highly skewed to the right, with discrete values (perhaps due to the limitations in the accuracy of the assessment equipment).  But note: library(fortunes) fortune('chicken') HTH ..... Peter Alspach -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Rich Shepard Sent: Tuesday, 15 May 2012 9:53 a.m. To: [hidden email] Subject: [R] Interpreting Q-Q Plots    My understanding of Q-Q plots is that if the tails of the plotted points fall above or below the x=y line the distribution of observed/measured values is under or over dispersed. But, how do I interpret measured values that are in horizontal lines? The attached plot illustrates this situation. TIA, Rich The contents of this e-mail are confidential and may be subject to legal privilege.  If you are not the intended recipient you must not use, disseminate, distribute or  reproduce all or any part of this e-mail or attachments.  If you have received this  e-mail in error, please notify the sender and delete all material pertaining to this  e-mail.  Any opinion or views expressed in this e-mail are those of the individual  sender and may not represent those of The New Zealand Institute for Plant and  Food Research Limited. ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: Interpreting Q-Q Plots

 On Tue, 15 May 2012, Peter Alspach wrote: > Probably highly skewed to the right, with discrete values (perhaps due to > the limitations in the accuracy of the assessment equipment). Peter,    Most of these data are near zero or the lower detection limit. A few values are very much higher. I didn't think of skewness as a reason. >  But note: > > library(fortunes) > fortune('chicken')    And since I don't have the experience, the only way to gain it is by learning from those with practice reading chicken entrails. Thanks, Rich ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.