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 Advanced Statistics Advanced Probability and Statistics Math Forum

December 4th, 2015, 01:50 PM   #1
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Joined: Nov 2015
From: japan

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Explain about chi-squared

Hello,
Could you explain why we have ? why alpha minus from 1 ?

The right in diagram have alpha/2 , and center is 1 - alpha, now the left of diagram 1 - alpha/2?!
Attached Images x201.JPG (8.2 KB, 12 views) x2.JPG (29.7 KB, 2 views)

Last edited by iranch; December 4th, 2015 at 01:56 PM. December 13th, 2015, 05:38 AM #2 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 The total area/probability under the curve (for any probability density curve) is 1. Two values have been chosen so that the area to the left of the first line is [math]\alpha/2[/imath] and to the right of the second line is $\displaystyle \alpha/2$. Of course, the area between the two lines is $\displaystyle 1- \alpha/2- \alpha/2= 1- \alpha$. The parts you are asking about seem to have the notation reversed. What I see in the graph is $\displaystyle \chi^2_{1-\alpha/2}(n-1)$ and $\displaystyle \chi^2_{\alpha/2}(n-1)$ when I think it should be $\displaystyle \chi^2_{n-1}= 1-\alpha/2$ and $\displaystyle \chi^2_{n-1}= \alpha/2$. That is because, typically, the subscript is the number of "degrees of freedom" minus 1, an integer. If I am correct then the first, $\displaystyle 1- \alpha/2$ is just the area/probability to the right of the first line, 1 minus the area/probability to the left. Thanks from iranch Tags chisquared, explain Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post bignick79 Algebra 9 June 29th, 2010 12:59 PM Shocker Advanced Statistics 1 February 8th, 2010 04:47 AM Tuneman Advanced Statistics 4 March 18th, 2009 10:37 AM cadman12 Advanced Statistics 1 March 27th, 2008 02:53 AM RFurball Advanced Statistics 1 September 10th, 2007 05:02 AM

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