AI-GEOSTATS On 19-May-06 Digby Millikan wrote: > Is it correct that the probability of being above or below > the mean of a skewed distribution is not necessarily 0.5?
Very much true that it may not be 0.5! As a general (though not absolutely true) rule, if a distribution is positively skewed then the mediam (0.5-point) is less than the mean, and for a negatively skewed distribution the median is greater than the mean. This often applies to the "staddard distributions" which turn up in practice. However, there is no general absolutely sure relationship between median and mean for non-symmetric distributions. Intuitively, the position of the median is independent of how you re-distribute the probability for values less than the median, and independent of how you re-distribute it for values greater than the median, so long as you keep 50% on either side. However, the mean is very much influenced by precisely where each bit of probability is located, so you can swing the mean around as much as you like without affecting the mediam. Best wishes, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 19-May-06 Time: 15:43:57 ------------------------------ XFMail ------------------------------ + To post a message to the list, send it to [email protected] + To unsubscribe, send email to majordomo@ jrc.it with no subject and "unsubscribe ai-geostats" in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list + As a general service to list users, please remember to post a summary of any useful responses to your questions. + Support to the forum can be found at http://www.ai-geostats.org/
