At 2:13 PM -0500 9/23/00, Paul Brandon wrote:
>At 10:10 AM -0500 9/23/00, Stuart Mckelvie wrote:
>>Dear Tipsters,
>>
>>One reason we use the standard deviation is that it comes from the
>>family of functions called moments about the origin of the
>>distribution:
>>
>>Moment (r) = E[(X - mean) to power r]
>>
>>(sorry that the program does not give proper symbols)
>>
>>So the first moment = E[X - mean] = E(x) - E(mean) = mean -mean = 0
>>
>>The second momen = E[(X - mean)squared] = variance
>>
>>The third mean reflect symmetry or skewness.
>
>This is probably the best answer yet.
>In physics, the first, second and third moments (I think; my reference is
>in my office and I'm not) correspond to frequency, rate and acceleration.
To update, I was referring to the position function, and its first and
second derivatives: velocity and acceleration (found my old Cliff's Notes
for Physics and Calculus ;-).
* PAUL K. BRANDON [EMAIL PROTECTED] *
* Psychology Dept Minnesota State University, Mankato *
* 23 Armstrong Hall, Mankato, MN 56001 ph 507-389-6217 *
* http://www.mankato.msus.edu/dept/psych/welcome.html *
