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mathematics help needed - how to calculate a mean?

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Author Topic:   mathematics help needed - how to calculate a mean?
mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005

mick Posts Only
Message 1 of 5 (380648)
01-28-2007 7:56 AM

Hi,
​
I know there are some mathy people here so I have a question.
​
I have a continuous function valid on the x axis within the domain -inifinity to infinity.
​
I want to calculate the mean value of y, within the range x0 to x1.
​
How do I do it?
​
for example, say I have an exponential distribution y=2e^(-2x)
​
From first principles, how would I go about calculating the mean of the curve between x=2 and x=3?
​
The function I am using in reality is a bit more complex with loads of parameters, but I am able to differentiate it and integrate it, if that is any help.
​
Thanks! It's driving me nuts!
​
Mick
​
Edited by mick, : No reason given.
Replies to this message:
 Message 2 by iceage, posted 01-28-2007 9:13 AM mick has replied
 Message 3 by cavediver, posted 01-28-2007 9:17 AM mick has not replied
  
iceage 
Suspended Member (Idle past 5940 days)
Posts: 1024
From: Pacific Northwest
Joined: 09-08-2003

iceage Posts Only
Message 2 of 5 (380654)
01-28-2007 9:13 AM 		Reply to: Message 1 by mick
01-28-2007 7:56 AM

Integrate over the interval and divide by the interval.
This message is a reply to:
 Message 1 by mick, posted 01-28-2007 7:56 AM mick has replied
Replies to this message:
 Message 4 by Chiroptera, posted 01-28-2007 10:23 AM iceage has not replied
 Message 5 by mick, posted 01-28-2007 9:12 PM iceage has not replied
  
cavediver
Member (Idle past 3669 days)
Posts: 4129
From: UK
Joined: 06-16-2005

cavediver Posts Only
Message 3 of 5 (380655)
01-28-2007 9:17 AM 		Reply to: Message 1 by mick
01-28-2007 7:56 AM

See Iceage's reply
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Chiroptera
Inactive Member

Chiroptera Posts Only
Message 4 of 5 (380667)
01-28-2007 10:23 AM 		Reply to: Message 2 by iceage
01-28-2007 9:13 AM

Pedantry is Freedom
Divide by the length of the interval.
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mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005

mick Posts Only
Message 5 of 5 (380800)
01-28-2007 9:12 PM 		Reply to: Message 2 by iceage
01-28-2007 9:13 AM

Thanks!
​
Kind of obvious when you think about it, but I'm no good at this stuff.
​
Cheers
This message is a reply to:
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